












































































































































































c 











X 



PRINCIPLES OF 


DYEING 






PRINCIPLES OF 
DYEING 


BY 

/i 

JL 

G: S. FRAPS, Ph.D. 

SOMETIME FELLOW, JOHNS HOPKINS UNIVERSITY 
ASSISTANT PROFESSOR OF CHEMISTRY, NORTH CAROLINA COLLEGE 
OF AGRICULTURE AND MECHANIC ARTS 


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Ncfo gfltk 

THE MACMILLAN COMPANY 

LONDON: MACMILLAN & CO., Ltd. 

1916 


All rights reserved 



Copyright, 1903, 

By THE MACMILLAN COMPANY. 


Set up and electrotyped January, 1903. 
Reprinted October, 1916. 


By 

NOV 16 


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Nartoooh 

J. S. Cushing & Co. — Berwick & Smith 
Norwood Mass. U.S.A, 



PREFACE 


This book is the result of two years’ instruction in 
dyeing, in the class room and in the laboratory. It aims 
to be a systematic presentation of the principles underlying 
the art of dyeing, illustrated and emphasized by laboratory 
exercises. It attempts to apply to the teaching of dyeing 
the same methods of class-room work, coordinated with 
experiments in the laboratory, which have proved so suc¬ 
cessful in the teaching of inorganic chemistry and other 
branches of science. 

The reader will not find in this book, therefore, a col¬ 
lection of recipes for the production of particular colors, 
or detailed descriptions of more than a few of the more 
important processes of dyeing, or even a list of the multi¬ 
tude of dyes which are at the service of the dyer. For 
information on these points, special works, or manuals of 
dyeing, must be consulted. A clear survey of the field 
of dyeing does not require these things; rather, a multi¬ 
tude of details would obscure the general view which it is 
desired to present. 

While intended primarily for the student, it is believed 
that this work will prove of benefit to the practical dyer 
who desires a fuller knowledge of the principles under¬ 
lying his art. The experiments hardly call for more 
apparatus and reagents than a dyer should possess for 
the purpose of making necessary tests of his dyes and 
chemicals. 


VI 


PREFACE 


The experiments, so far as is practicable, are the pro¬ 
cesses used in dye-house work ; necessarily modified for 
use as laboratory experiments. It has seemed desirable 
to reduce the time of the operations, so as to admit of the 
performance of a larger number of experiments by the 
student in the time at his disposal. Samples of all dyed 
material should be pasted in a suitable scrap-book, and 
marked with the name of the dye and the process used 
for dyeing. The dyed samples used for fastness tests, 
and all other samples possible, should be entered in the 
scrap-book and suitably marked, so that the pages of the 
scrap-book will exhibit a complete record of the student’s 
work. In addition, a note-book should be kept, with 
descriptions of the experiments, observations, results, and 
answers to questions, after the manner of note-books used 
for experimental inorganic chemistry. 

Before entering on this course, all students should be 
tested for color-blindness. 

In the preparation of this book, a number of books and 
original articles have been consulted. It is impossible to 
make special acknowledgment to all of these, but the fol¬ 
lowing deserve particular mention : Knecht, Rawson, and 
Lowenthal’s “ Manual of Dyeing,” Hummel’s “ Dyeing of 
Textile Fabrics,” Paterson’s “Science of Color Mixing,” 
Gardner’s “ Mercerization der Baumwolle,” Beech’s “Dye¬ 
ing of Cotton Fabrics,” and the publications of the Cassela 
Color Company, the Farbewerke Hoechst (Victor Koechl, 
United States agent), the Berlin Aniline Works, and the 
Farbenfabriken von Elberfeld. Acknowledgment is due 
also to Messrs. P. R. French and E. B. Owen for reading 
manuscript and proofs, and Professor W. A. Withers and 
Professor D. H. Hill for suggestions. 

Raleigh, North Carolina, 

September 1902. 


CONTENTS 


CHAPTER I 

PAGE 

Introduction .i 

Object of the Dyer — Laws of Dyeing — Textile Fibers —Animal 
Fibers — Vegetable Fibers — Artificial Fibers — Coloring Matters 
— Plan of Study. 


CHAPTER II 

Congo Red — Primuline.7 

Congo Red — Properties — Action of Acids — Reduction of 
Congo — Behavior to Fibers — Function of the Salts in Dyeing — 
Action of Hard Water — Hard Water — Stripping of Congo — 
Behavior to Washing, Light, etc. — Fastness — Direct Cotton Colors 
— Primuline — Properties — Behavior toward Fibers — Diazotizing 
and Developing — Precautions in Diazotizing — Developers — Fast¬ 
ness of the Colors — Summary. 

CHAPTER III 


Fuchsine.20 

Composition — Properties — Leuco Compounds — Rosaniline 
Tannate — Other Salts — Action toward Fibers — Dyeing Cotton 
with Fuchsine — Mordants — Fixing Tannic Acid — Action of 
Hard Water — Printing Fuchsine — Basic Colors. 


CHAPTER IV 

Biebrich Scarlet — Alkali Blue.29 

Properties — Action toward Fibers — Action of the Acid — 
Assistants — Stripping Biebrich Scarlet — Dyeing Cotton — Hard 
Water—Alkali Blues — Composition — Properties—Action toward 
Cotton and Wool — Acid Colors. 

vii 





CONTENTS 


Vlll 


CHAPTER V 


Logwood. 

Preparation — Composition — Properties — Salts — Action tow¬ 
ard Fibers — Behavior of Fibers to Mordants — Polygenetic Colors 
— Assistants for Metallic Mordants — Methods for Dyeing with 
Logwood — Saddening — Soaping — Application of Logwood — 
Mordant Colors. 


CHAPTER VI 

Indigo — Chrome-yellow. 

Indigo — Preparation — Composition — Artificial Indigo — Prop¬ 
erties — Reduced Indigo — Dyeing with Indigo — Fastness of 
Indigo — Indigo Extract — Chrome-yellow — Production — Prop¬ 
erties— Retrospect — Theory of Dyeing —Classes of Fibers. 

CHAPTER VII 

Vegetable Fibers — Cotton. 

Vegetable Fibers — Cotton — Motes — Grades of Cotton — 
Microscopic Appearance — Dead Cotton — Other Defects — Com¬ 
position — Cellulose — Preparation and Properties — Solvents for 
Cellulose — Cellulose Nitrates — Oxycellulose — Action of Acids — 
Carbonization — Action of Alkalies — Mercerization — Nature of 
the Change—Properties of Mercerized Cotton — Tendering of 
Cotton — Cotton Manufacture. 


CHAPTER VIII 

Linen — Other Vegetable Fibers. 

Linen — Microscopic Appearance — Composition — Properties 
— Detection of Cotton in Linen — Jute — Composition and Prop¬ 
erties — Hemp — China Grass — Other Fibers — Other Vegetable 
Materials. 


CHAPTER IX 

Animal Fibers — Wool. 

Animal Fibers — Wool — Grades — Microscopic Appearance — 
Kemps — Physical Properties — Composition of Raw Wool — 
Composition of the Fiber — Solution of Wool — Chlorinated 




CONTENTS 


IX 


PAGE 

Wool — Oxidation of Wool — Tendering of Wool — Absorptive 
Power—Behavior to Dyes — Detection of Wool — Carbonization 
— Shoddy and Mungo — Rare Wools — Wool Manufacture. 

CHAPTER X 

Silk ............. 90 

Silk — How the Worm Spins — Preparation of Silk — Grades of 
Silk — Physical Properties — Composition — Solution of Silk — 
Absorptive Power — Metallic Salts — Coloring Matters — Tender¬ 
ing of Silk — Oxidation of Silk — Estimation of Silk, Wool, and 
Cotton — Wild Silks — Composition and Properties of Tussur Silk 
— Detection of Tussur Silk. 

CHAPTER XI 

Operations Preliminary to Dyeing — Bleaching Cotton and 

Linen.98 

Objects — Wetting out — Bleaching — Chemistry of Bleaching 
— Saponification — Methods — Decolorization — Decolorizing 
Agents — Oxycellulose — Bleaching Loose Cotton — Yarn Bleach¬ 
ing— Cop Bleaching — Preparing the Chemic — Control of the 
Chemic — Titration of the Chemic — Control of the Sour — Cloth 
Bleaching — Printer’s Bleach — Market Bleach — Turkey-red 
Bleach — Defects in Bleached Goods—Other Bleaching Processes 
— Linen Yarn — Linen Cloth — Jute Bleaching. 

CHAPTER XII 

Wool and Silk Scouring and Bleaching.120 

Washing Loose Wool — Methods and Machinery — Soaps — 
By-products — Other Methods of Wool Washing — Yarn Scouring 
— Methods and Machinery — By-products — Cloth Scouring — 
Crabbing — Wool Bleaching—Sulphur Bleach—Hydrogen Per¬ 
oxide Bleach — Silk — Methods of Boiling-off — Bleaching — Souple 
Silk — Other Operations — Weighting of Silk. 

CHAPTER XIII 

Dyeing Machinery and Manipulations.133 

Raw Stock — Dyeing — Washing — Drying — Sliver or Slubbing 
— Skeins — Pland Dyeing — Machine Dyeing — Washing — Ex- 




X 


CONTENTS 


PAGE 

tracting Water — Drying — Warps — Dyeing Machines — Sizing 
— Drying — Dyeing on the Cop — Cloth — Drying — Printing of 
Slubbing and Warps. 


CHAPTER XIV 

General Observations on Dyeing. 150 

Dissolving the Dye — Hard Water—Water Purification — Pro¬ 
duction of Level Dyeings — Feeding of Colors — Standing Baths 
— Mixing of Dyes — Dyeing to Shade — Fastness of Dyes—Re¬ 
quirements for Fastness — Defects in Dyeing — Soaping — Silk 
Dyeing. 


CHAPTER XV 


Direct Cotton Colors . . . . .164 

Properties — Application to Cotton — Methods of Dyeing — 
Assistants — Production of Level Colors — Mixing Direct Cotton 
Colors — Exhaustion of the Bath — Standing Baths — After-treat¬ 
ment of Direct Cotton Colors — Diazotizing and Developing — 
Control of the Diazotizing Bath — Developing — Application — 
Shading Developed Dyeings — Coupling — After-treatment with 
Metallic Salts — Application — Defects in Dyeing — Sulphur Colors 
— Properties — Methods of Dyeing — After-treatment — Soaping — 
Defects in Dyeing — Topping Direct Cotton Colors with Basic Colors 
— Fastness of Direct Cotton Colors — Application to Linen — Ap¬ 
plication to Wool — Application to Silk — After-treatment. 


CHAPTER XVI 


Basic Colors.183 

Composition — Properties — Application to Cotton — Tannic 
Acid — Salts — Affinity for Cotton — Antimony Salts — Mordanting 
with Tannic Acid — Fixing Tannic Acid — Dyeing — Janus Colors 
— After-treatment with Tannic Acid—Mordanting with Turkey- 
red Oil and Soap — Alum Mordant—Dyes as Mordants — Fastness 
of the Colors — Defects in Dyeing — Basic Colors on Wool — 
Dyeing — Sulphur Mordant — Fastness of the Colors — Defects 
— Basic Colors on Silk — After-treatment. 




CONTENTS 


XI 


CHAPTER XVII 

PAGE 

Acid Colors. 

Properties — Application to Cotton — Methods of Dyeing — 
Application to Jute—Application to Wool —Methods of Dyeing 
— Alkali Colors — Level Dyeing — Mixing — Exhaustion of Bath 
— Defects in Dyeing — Fastness — Acid Dyes on Silk — Methods 
— Alkali Colors. 


CHAPTER XVIII 

Mordant Dyestuffs.202 

Methods of Application — Natural Mordant Colors — Artificial 
Mordant Dyestuffs — Mordant Colors on Cotton — Alizarin — 
Methods of Application — Turkey-red Processes — New Turkey-red 
Process — Alizarin-red Processes — Alizarin on Chromium Mor¬ 
dants— Alizarin on Iron Mordants — Logwood — Defects — Cutch 
— Other Mordant Colors — Mordant Dyestuffs on Linen — Mor¬ 
dant Colors on Wool — Ordinary Mordant Colors — Mordanting 
with Aluminium — Mordanting with Chromium — Dyeing — Sad¬ 
dening— Level Dyeing — Defects in Dyeing—Single-bath Method 
— Mixing — Logwood — Acid-mordant Colors — Mixing and Shad¬ 
ing— Mordant Colors on Silk — Mordanting — Dyeing. 


CHAPTER XIX 

Insoluble Colors.221 

Oxidation Colors —Aniline Black — Properties — Application — 
Production on Loose Cotton and Yarn — Production on Cloth — 
Topping Aniline Black — Soaping — Defects in Dyeing — Indigo 
— Application to Cotton — Dyeing — Topping Indigo—Applica¬ 
tion to Wool — Insoluble Azo Colors — Paranitraniline Red — 
Soaping — Defects — Other Azo Colors — Mineral Colors — Manga¬ 
nese Brown — Iron-buff and Nankin Yellow — Prussian Blue. 


CHAPTER XX 

Mercerization — Artificial Silk.235 

Mercerization — Production of Embossed Effects — Production 
of Lustered Cotton — Process of Mercerization — Machines for 
Mercerization —Properties of Lustered Cotton — Dyeing Mercerized 





CONTENTS 


Xll 


PAGE 

Cotton — Direct Cotton Colors — Basic Colors — Scroop Feel — 

Level Dyeing — Artificial Silk — Cellulose Silk — Properties — 
Dyeing — Detection — Gelatin Silk. 


CHAPTER XXI 

Dyeing of Union Goods.242 

Dyeing Cotton-wool Goods — Dyeing with Direct Colors — Appli¬ 
cation — Acid Dyes — Basic Colors — Shoddy Dyeing — Cotton 
and Silk — Wool and Silk — Methods of Dyeing. 

CHAPTER XXII 

Dye Mixing—Dye Testing.250 

The Solar Spectrum — Absorption-spectrum — Dichroism — 
Primary, Secondary, and Complementary Colors — Hue, Tint, Shade, 

Purity — Absorption-spectrum of Mixtures — Primary and Secondary 
Mixing-colors — Mixing of Dyes—Effect of Light on Colors — 
Color-blindness — Dye Testing — Comparative Dye-trials — Test¬ 
ing for Mixtures — Detection of Dyes. 



LIST OF ILLUSTRATIONS 


FIGURE PAGE 

1. Cotton. . 

2. Linen.. 

3. Wool.. 79 

4. Low-pressure Kier . . . .. . 

5. Bleaching under Sieve . io 8 

6. Cloth-washing Machine.H3 

7. Square Beater Washing Machine.115 

8. Cloth-scouring Machine.124 

9. Klauder-Weldon Raw Stock Dyeing Machine . . .134 

10. Raw Stock Drying Machine.133 

11. Klauder-Weldon Skein-dyeing Machine.138 

12. Skein-washing Machine.139 

13. Hydro-extractor.141 

14. Warp-dyeing Machine.143 

15. Drying Cans.144 

16. Dye-beck and Wince.145 

17. Jiggers.146 

18. Padding Machine.147 

19. Single-color Printing Machine.148 

20. Aniline Black Ageing Chamber.226 

21. Solar Spectrum.251 

22. Absorption Spectrum of a Yellow Dye ( A ), a Blue Dye ( B ), 

and the Mixture of the Two (C).254 


Xlll 






















I 

















PRINCIPLES OF DYEING 


CHAPTER I 

INTRODUCTION 

The term “dyeing,” in its broad sense, covers the color¬ 
ing of leather, paper, feathers, and other articles, besides 
the coloring of textile fabrics. 

This book will be confined to a discussion of the dyeing of 
textile fibers, both the raw material and the finished fabric. 

Object of the Dyer. — The object of the dyer is to pro¬ 
duce any desired color on the material given him, an object 
usually accomplished by means of dyes, but sometimes by 
the use of bleaching agents, such as in the case of the 
production of a white piece of goods. The dyer is usually 
furnished with a sample of goods of the exact shade desired; 
but besides matching the sample, the color he produces 
must come up to certain requirements as regards fastness, 
cost, etc. In some cases it does not matter if the color 
washes out with water, provided it resists the action of 
light; while in other cases the color must be as fast to 
soap and hot water as possible. These requirements are 
met by the selection of different dyes and methods of dye¬ 
ing, according to the demands of the work. 

The color produced by the dyer must also be such that 
it will not undergo undesirable changes during the further 


B 


i 


2 


PRINCIPLES OF DYEING 


manufacture of the goods, or in any of the finishing pro¬ 
cesses to which they may be subjected. For example, the 
color must not rub off from dyed threads to uncolored 
threads, giving the goods a dirty appearance, or change 
while the goods are being dried or ironed. 

Laws of Dyeing. — The laws of dyeing rest, on the one 
hand, on the chemistry and physics of the dyes and textile 
fibers, and, on the other hand, on the principles involved 
in the application of the dye to the fiber. The different 
textile fibers have their individual peculiarities, and differ 
in their behavior toward the same dye; processes which 
are beneficial to one fiber may be positively injurious to 
another. Dyes also differ greatly in their behavior to fibers, 
and require different methods of application according to 
their nature. 

y 

Textile Fibers. — Cotton, wool, silk, linen, etc., are known 
as textile fibers. The only common property of all the 
textile fibers is their fibrous nature. They are divided into 
three groups: — 

I. Mineral fibers ; examples, asbestos, glass wool, and 
slag-wool. 

II. Animal fibers; examples, silk and wool. 

III. Vegetable fibers; examples, cotton, linen, and jute. 

Mineral Fibers are incombustible; they are never dyed 
or bleached, and are only mentioned for the sake of com¬ 
pleteness. Asbestos is a natural silicate of calcium and 
magnesium, and, on account of its being a non-conductor 
of heat, is used principally as a covering for steam-pipes. 
Glass wool is spun glass. Slag-wool y obtained by blowing 


INTRODUCTION 


3 


a strong current of air through a stream of molten slag, is 
used for covering steam-pipes. 

Animal Fibers. — Silk and wool are the two principal 
members of the group; wool is the outer covering of the 
sheep, and silk is the product of a caterpillar. The animal 
fibers contain carbon, hydrogen, nitrogen, and oxygen; 
wool contains sulphur in addition. In their action toward 
dyes and in other of their properties, animal fibers are quite 
different from vegetable fibers, as will be brought out later. 

Leather, feathers, bone, horn, and ivory resemble the 
animal fibers in many of their properties, and behave in a 
similar way to dyes. 

Vegetable Fibers. — Most of the vegetable fibers are 
obtained from the stem or leaves of plants, but the most 
important one — cotton — consists of the hairs which sur¬ 
round the seeds of a species of plant (Gossypium). The 
vegetable fiber next in importance to cotton is linen, then 
come hemp, jute, and China grass. The vegetable fibers 
contain carbon, hydrogen, and oxygen, but no nitrogen or 
sulphur. They do not have as much chemical activity as 
the animal fibers. 

Straw (for hats), vegetable ivory (for buttons), wood, and 
paper resemble the vegetable fibers in their properties, and 
may be placed in the same class. 

Artificial Fibers. — Imitation silks, spun artificially, have 
attained some commercial importance. They will be dis¬ 
cussed later. 

Coloring Matters. — According to their origin, coloring 
matters may be divided into two classes — natural and 
artificial. 


4 


PRINCIPLES OF DYEING 


The natural colors are of vegetable or of animal nature, 
though the only animal dye of any importance is cochineal, 
which is found in a bug. 

Until about fifty years ago, the dyer was obliged to rely 
entirely upon natural colors, and some few mineral colors, 
to produce the effect desired. In 1856 the first artificial 
color (mauveine) was manufactured byW. H. Perkins, and 
captivated the world by its purity and beauty. Soon others 
were prepared, and a very large number of highly colored 
organic compounds are now known, though they do not all 
find practical application as dyes. The number of artificial 
dyes is increasing so rapidly every year that it is difficult to 
keep up with the new dyes which are constantly being put 
on the market. 

Another advance made in recent years has been the dis¬ 
covery of methods for the preparation of natural coloring 
matters in the factory, the first one so prepared being 
alizarin. Alizarin is the coloring principle of the madder 
plant, which had been used for a long period to produce a 
fiery red color upon cotton goods. At present the arti¬ 
ficial color has replaced the natural one almost completely. 
Indigo, a very important blue dye, is another natural dye 
which is being prepared by chemical methods, and just now 
there is a decided competition between the natural indigo 
and the artificial or synthetic indigo. 

Plan of Study. — At present an enormous number of 
coloring matters are known, and the number is increasing 
rapidly. The matter is still further complicated by the fact 
that the same dye is often sold under several different names, 
and in different degrees of purity. The large number of 


INTRODUCTION 


5 


dyes known need not, however, be a source of uneasiness 
to the student. The dyer does not need to be acquainted 
with every individual color, but should have a knowledge 
of the most important colors, and know how to test new 
dyes and work out new processes. 

Without regard to their origin or chemical constitution, 
coloring matters can be separated into a number of groups 
for convenience in study, just as we can separate the ele¬ 
ments into groups; as, for example, the chlorine group, 
including chlorine, bromine, and iodine ; the oxygen group, 
in which are included sulphur, selenium, and tellerium. 
The members of these groups have certain resemblances 
to each other, and also their peculiarities, which distinguish 
them from the other members. 

It is the object of this work to present a clear view of 
the subject of bleaching and dyeing of textile fibers. It is 
proposed to consider only a comparatively small number 
of dyes, either important in themselves, or those which can 
be used to emphasize important principles. In general, 
detailed information regarding particular dyes will not be 
given. It would hardly be profitable for the beginner to 
burden his mind with too many details at first, — he may 
thereby lose the general view, which it is important that he 
should gain quickly. Nevertheless, seemingly unimportant 
details, neglect of which may make or mar the work of the 
dyer, have been emphasized. It is the attention to details, 
which must be learned, and learned well, which makes the 
good dyer. 

The plan of study which will be followed is briefly this : — 

Of the first group of dyes, two will be studied with special 
attention to their action toward the different fibers. Mem- 


6 


PRINCIPLES OF DYEING 


bers of the second group of dyes will then be taken up, and 
so on, until all the groups have been considered. 

A clear idea of the relations between the groups of dyes, 
their general properties, and their behavior toward different 
fibers having been gained in this way, the next step will be 
the study of the groups of textile fibers. 

Following this will come the consideration of the ma¬ 
chinery for dyeing and bleaching, and the methods of pre¬ 
paring the fibers or fabrics for the dyeing proper. Finally 
the different groups of dyes will be studied, with the prin¬ 
ciples involved in their application to the different classes 
of material. 


CHAPTER II 


CONGO RED-PRIMULINE 

Congo red, or congo, was discovered in 1884, and was 
the first artificial dye known to have the property of dyeing 
cotton directly without the aid of any other substance. For 
this reason other dyes of the same kind, which were after¬ 
ward discovered, are sometimes called congo colors. 

Properties. — Congo red is a red-brown powder, readily 
soluble in water. Its solubility is decreased by the presence 
of salts, — such as common salt (sodium chloride) or Glau¬ 
ber’s salt (sodium sulphate). Salt in sufficient quantity will 
precipitate the dye from solution. 

Experiment i. — Dissolve a little congo red in 200 cc. water. 
Add common salt to a portion of the solution, stirring from time to 
time, until no more dissolves. Let the solution stand for half an 
hour, stirring occasionally, and filter. The first few drops may be 
colored, but the remainder of the filtrate will be nearly colorless. 
The dye has been “ salted out ” from solution. 

Practical application is made of the power of salts to pre¬ 
cipitate dyes and other compounds from solution in the 
manufacture of dyestuffs and other substances. In dyeing 
with congo and similar colors, salts are usually added to the 
dye-bath to decrease the solubility of the dye, and cause 
more of it to go upon the fiber. 


7 


8 


PRINCIPLES OF DYEING 


Action of Acids. — Congo is the sodium salt of a dibasic 
acid. If we add hydrochloric acid to a solution of congo, 
the free color acid (combined with hydrochloric acid) sepa¬ 
rates as a dark-blue, flocculent precipitate. The reaction 
is as follows : — 

C 32 H 22 N 6 S 2 0 6 Na 2 + 2 HC 1 = C 32 H 22 N 6 S 2 0 6 H 2 + 2 Na Cl. 

Congo red. Color acid. 

Or, if we let Ac Na 2 represent Congo red, the reaction may 
be written in a condensed form : — 

AcNa 2 + 2 HC 1 = AcH 2 + 2 Na Cl. 

Ac merely stands for a complex group of atoms of acid 
nature. 

If the blue precipitate is treated with sodium hydroxide, 
it dissolves, Congo red being formed again. 

Experiment 2.—Add hydrochloric acid to a solution of congo 
red. Explain what happens, and write condensed reaction. 

The acids always present in the air, especially in the air 
of cities, cause the bright color of goods dyed with congo to 
become dull gradually by liberating the free color acid; an 
effect which can be counteracted, to a certain extent, by 
saturating the goods, before drying, with a solution of 
sodium carbonate, which neutralizes the acid. 

Reduction of Congo. — Reducing agents, such as zinc 
dust and acetic acid, transform congo red into colorless 
bodies. 

Experiment 3. — To about 20 cc. of a solution of congo red 
add 20 cc. acetic acid (25 per cent) (what happens?), and then 
about 5 g. zinc dust. Mix well, heat to boiling, and boil a few 
minutes= Filter. Explain results. 


CONGO RED — PRIMULINE 


9 


The reaction between acetic acid and zinc dust is as 
follows : — 

2 HC 2 H 3 0 2 + Zn == Zn(C 2 H 3 0 2 ) 2 + 2 H. 

Acetic acid. Zinc acetate. 

The nascent hydrogen is taken up by congo red, and 
splits it into two new colorless compounds. All organic 
coloring matters may be reduced to colorless compounds by 
suitable choice of reducing agents. They vary greatly in 
the ease with which the reduction may be effected. 

Behavior to Fibers. — If we boil cotton or wool with a 
solution of congo red, the fiber will withdraw a portion of 
the dye from solution, and become colored. Further, the 
color cannot be washed out with water. The dye has an 
affinity for the substance of the fiber, and dyes it; such 
dyes are called direct colors or substantive colors. 

Experiment 4. — Boil five 10-gram skeins of cotton yarn with 
500 cc. water and 1 g. sodium carbonate until they are thor¬ 
oughly wet. Wash them and place them in clean water until 
needed. Cotton yarn should always be “ boiled off” or “wetted 
out ” before dyeing. 

Prepare a dye-bath with 2 per cent (of the weight of the yarn) 
congo red, 1 2 per cent sodium carbonate, and 20 per cent Glau¬ 
ber’s salt (sodium sulphate), and make the volume up to 200 cc. 
Hang a 10-gram skein of cotton yarn in the bath on a V-shaped 
glass rod, and boil gently half an hour, working the yarn from time 
to time by lifting it out of the cup, and turning it with the aid of a 
glass rod. Remove, rinse, and dry. Save the dye-bath. 

1 To save time, dyes and salts are furnished in solution, so that the student 
has only to measure out a certain volume of liquid. For example, 25 cc. congo 
solution contains 0.1 g.; 10 cc. sodium carbonate solution contains 0.1 g.; 
sodium sulphate (anhydrous) 5 cc. = 0.1 g. The dyeings are usually made in 
agate-ware cups, ppint capacity, heated directly by the burner. 


10 


PRINCIPLES OF DYEING 


Dye a 5-gram skein of wool in the same way, without the 
sodium carbonate. Which skein is the darker? Compare the 
dye-baths. Which fiber takes up the more dye ? 

If we examine the two solutions after dyeing cotton and 
wool with congo, we find : — 

1. The wool has exhausted the dye-bath ; that is, it has 
withdrawn almost all dyestuff from solution. 

2. The cotton has not exhausted the bath, but has left a 
considerable portion of the dye unabsorbed. 

The experiment illustrates the characteristic differences 
between animal and vegetable fibers in their behavior 
toward direct dyes. Animal fibers, represented by wool, 
have a great affinity for direct colors, and withdraw them 
readily and completely from solution. Vegetable fibers 
have no great affinity for them, and rarely exhaust a dye- 
bath. 

It is evident that if we throw away the dye-bath after 
dyeing cotton with Congo red or similar colors, a part of 
the dye is lost. In dyeing with such colors, the dye-bath 
is used continuously whenever possible, its strength being 
restored by fresh additions of dyestuff and salts after each 
dyeing. 

Function of the Salts. — In dyeing with congo red and 
similar colors, salts are always added to the dye-bath. 

Glauber’s salt or common salt is added to decrease the 
solubility of the dye, and thereby cause more of it to go 
on the fiber. Sodium carbonate is added to make the bath 
alkaline and to counteract to some extent the action of 
acids of the air, as the sodium carbonate is not entirely 
washed out. 


CONGO RED — PRIMULINE 


I I 

Action of Hard Water. — The calcium and magnesium 
salts of the color acid of Congo red are not soluble in 
water, and are precipitated when a calcium or magnesium 
salt and congo red are brought together in solution. 

Water containing calcium salts (hard water), when used 
for the preparation of a dye-bath, precipitates Congo red 
with loss to the dyer. 

Experiment 5. — Dissolve 0.1 g. congo in 75 cc. water, add 
25 cc. lime-water, and boil about 10 minutes. What is the pre¬ 
cipitate? 

Prepare two dye-baths, each with exactly 2 per cent congo 
(measure the solution with a pipette), 2 per cent sodium carbon¬ 
ate, and 20 per cent sodium sulphate. Add 50 cc. lime-water to 
one solution and make the volume of each 200 cc. Dye two 
skeins of cotton yarn (boiled out) as described in Experiment 4. 
What is the effect of hard water? 

Hard Water. — The purest water found in nature is rain¬ 
water. As soon as rain-water comes in contact with the 
earth, and begins its course toward the ocean, it begins to 
take up various substances, according to the character of 
the soil with which it comes in contact. Natural waters 
which come in contact with limestone (calcium car¬ 
bonate) gradually take up more or less of the carbonate 
with the aid of the carbonic acid of the air, forming cal¬ 
cium acid carbonate, Ca(H C 0 3 ) 2 , and becoming hard. On 
heating the water, this salt decomposes, carbon dioxide 
is given off, and calcium carbonate is precipitated. The 
hardness removed by boiling is called the temporary 
hardness. 

Water, when it comes in contact with calcium sulphate, 
dissolves it, and a hard water is produced, the hardness of 


12 


PRINCIPLES OF DYEING 


which is not removed by boiling, and is therefore called 
permanent hardness. Magnesium sulphate acts in the same 
way to produce permanent hardness. 

By boiling hard water with sodium carbonate or soap, 
insoluble calcium compounds are precipitated and soft 
water can be drawn off. These, and other methods of 
purifying water, will be discussed later. 

Hard water is often injurious in dyeing. 

Stripping of Congo. — When cotton yarn dyed with congo 
is boiled in water, part of the color will be removed or 
stripped from the fiber. 

Experiment 6. — Plait part of the cotton yarn dyed with congo 
with undyed cotton yarn, place it in 50 cc. water, and boil 15 
minutes. Proceed with dyed wool in the same way, plaiting it 
with wool yarn. Which fiber loses its color more easily? 

The experiment shows that the color is more easily 
stripped from cotton than from wool. It also shows, in 
the case of the cotton yarn, that part of the color stripped 
off is taken up by undyed fibers; the dyed and undyed 
yarn will become the same color if boiled long enough 
with water. 

Behavior to Washing, Light, etc. — If we subject the 
dyed yarn to the action of warm water and soap, — that is, 
imitate the action of washing, — the solution becomes 
colored, but the color of the yarn does not fade appreci¬ 
ably. If white material is present, it becomes colored ; the 
color is said to bleed. 

Experiment 7. — The test for fastness to washing is conducted 
as follows : — 


CONGO RED—PRIMULINE 


13 


Plait part of the dyed cotton with undyed yarn. Make up a 
solution 1 of 10 g. soap in a liter of water, heat to 6o° C., and 
pour about 25 cc. on the yarn. The plait should be worked 
and squeezed in the liquid, and allowed to remain in it 10 minutes. 
It is then rinsed in cold water, allowed to lie in water 15 minutes, 
then wrung out, washed, and dried. Note any change in the color 
of the yarn, how much color is taken up by the soap, and whether 
the color bleeds. Test the dyeing on wool in the same way. 

Congo is much faster to washing on wool than on cotton. 

If a skein of yarn dyed with Congo is placed in the sun¬ 
shine, after a time the color will fade. In time the color 
would be almost completely destroyed. All dyes are 
affected by light, but vary in their resistance toward it; 
the nature of the material dyed (cotton or wool, etc.) is also 
of effect. 

Experiment 8. — Expose some of the dyed yarn to direct sun¬ 
shine for several days. 

Dyes are also tested for their fastness to acids. The 
test represents their resistance to acids of the air, and per¬ 
spiration. 

Experiment 9. — Steep portions of the dyed yarns in about 10 
cc. of a 25 per cent solution of acetic acid for about 5 minutes. 
Wring out, wash, and dry. Explain any change in color. 

Another test is for fastness to alkalies : — 

Experiment 10. — Steep portions of the dyed yarn for 5 minutes 
in 25 cc. of a 1 per cent solution of sodium carbonate, wash and dry. 

Fastness. — By the fastness of a color to washing, we 
mean its permanence when subjected to friction, and the 
action of a warm solution of soap (Experiment 7). In the 

1 A warm solution of soap for this test should be kept on hand in the 
laboratory. 


14 


PRINCIPLES OF DYEING 


same way we speak of fastness to light, to acids, to alkalies, 
and to other influences. According to the behavior of the 
color, it is characterized as fugitive (easily affected), mod¬ 
erately fast, fairly fast, and very fast. 

The term “fast,” as applied to a piece of goods, means 
that the color will not fade under ordinary usage. What 
will be required of the color depends upon the use to which 
the material is to be put. The color of a shirt must be fast 
to washing and light; coat linings may not be washed, but 
the color must not rub off. Underwear must be fast to 
perspiration and washing. Carpets and curtains must with¬ 
stand the action of light. It is perfectly plain that a dye 
may be very fast when applied to one class of material, and 
fugitive when applied to another class. 

Direct Cotton Colors. — Congo is a member of a class of 
dyes known as direct cotton colors, or substantive cotton 
colors, which will dye cotton, wool, or any other fibre with¬ 
out the aid of other substances. There are dyes which are 
direct colors for wool and silk, but not for cotton; hence 
these dyes are called direct cotton colors. 

The direct cotton colors, as a rule, resemble Congo in 
their behavior toward acids, alkalies, salts, hard water, and 
the textile fibers. They are dyed in much the same way, 
as a rule “ bleed ” into white material, and are faster in 
wool than in cotton. Cotton never removes these colors 
completely from the dye-bath. 

Primuline. — Primuline is a direct cotton color which was 
discovered in 1888. It is sometimes called carnotin, poly- 
chromin, and aureotin. Thiochromogen is claimed to be a 
very pure form of primuline. 


CONGO RED —PRIMULINE 


15 


Properties. — Primuline is a yellow powder, readily solu¬ 
ble in hot water, less soluble in cold. Like Congo, it can 
be “salted out” of solution by sodium sulphate, sodium 
chloride, or other salts. 

Like Congo, primuline is the sodium salt of a color acid. 
The free acid is precipitated as a dark yellow flocculent 
mass when hydrochloric acid or sulphuric acid is added to 
a solution of the dye. 

Experiment ii. — Dissolve a little primuline in water. Salt 
out a portion of the solution as in Experiment 1. To another 
portion of the solution add hydrochloric acid, and heat gently. 
The precipitate is the free color acid. 

When primuline is dissolved in concentrated sulphuric 
acid, it forms a liquid, which appears yellow if the light 
which reaches the eye passes through the solution, blue 
if it is reflected from the surface of the liquid. It has a 
blue fluorescence. If the solution is poured into water, an 
orange-yellow precipitate is formed. 

The behavior of dyes toward concentrated sulphuric acid 
is a useful aid in their identification. The test is carried 
out as follows : — 

Experiment 12. — Dissolve a small quantity of primuline in con¬ 
centrated sulphuric acid, and note the color of the solution. Pour 
a portion of it into water. Heat another portion nearly to boiling, 
observing any changes, and (caution!) pour it into cold water. 

Behavior toward Fibers. — Primuline is dyed on cotton, 
like Congo red, in a bath with the addition of salts. It dyes 
a greenish yellow color, which is somewhat faster to washing 
than congo. The bath is not exhausted. 

The direct dyeings of primuline are of little interest. It 
is usually converted into other dyes by a process called 
diazotizing and developing. 


i6 


PRINCIPLES OF DYEING 


Diazotizing and Developing. —«- When goods dyed with 
primuline are treated first with a solution of nitrous acid, 
and then with a developer, new dyes are produced with 
new properties. They are insoluble in water, and valuable 
on account of being fast to washing. The process is called 
diazotizing and developing. 

Direct cotton colors and other bodies which can be diazo- 
tized and developed contain the group NH 2 . They are 
related to ammonia, and may be regarded as ammonia in 
which one atom of hydrogen has been replaced by a com¬ 
plex group of atoms, as C 6 H 5 NH 2 , aniline. When these 
substances are treated with nitrous acid, the two combine 
to form a diazonium salt: — 

C 6 H 6 NH 2 HC 1 + HN 0 2 = C 6 H 5 N 2 C 1 + 2 H 2 0 ; 

Aniline hydrochloride. Phenyl diazonium chloride. 

or, for any of these compounds : — 

RNH 2 HCl + HN 0 2 =RN 2 Cl + 2 h 2 o. 

Diazonium compounds are, for the most part, very un¬ 
stable, and even explosive in the solid state. Many of 
them decompose when the temperature is raised, and they 
easily enter into reactions. 

When a diazonium salt is treated with a phenol, or an 
aromatic amine, under proper conditions, the two combine 
directly and a stable compound is formed. For example:— 

C 6 H 5 . N 2 .Cl + C 6 H 5 OH = C 6 H 6 .N 2 C 6 H 4 OH + HC 1 . 

Diazonium chloride. Phenol. Azoxy benzene. 

This is the kind of action which takes place when a 
diazotized fabric is treated with a developer. The de¬ 
veloper combines with the diazonium compound to form 
a more stable body, which is a new dye. 


CONGO RED —PRIMULINE 


17 

Experiment 13. — Dye five 10-gram skeins of boiled-out 
cotton yarn with primuline, as follows : Dissolve 4 per cent (of 
the weight of the yarn) primuline, 30 per cent salt, and 5 per 
cent sodium carbonate in 600 cc. water; heat, enter the yarn, and 
boil 30 minutes. Work from time to time. Is the bath exhausted? 

Diazotize four of the dyed skeins. Prepare a bath of 3 per 
cent sodium nitrite and 200 per cent dilute hydrochloric acid in 
600 cc. water. Free nitrous acid is liberated according to the 
reaction : NaNCb + HC 1 = NaCl -f- HN 0 2 . Enter the yarn, and 
work 10 minutes. The diazotized primuline is very unstable, and 
must be developed as soon as possible. Rinse, and develop as 
described below. 

Hang one skein of the yarn, after diazotizing and before de¬ 
veloping, in the sunshine for 10 minutes, and then develop as in 
(a) below. 

Developing. Have ready the following baths, enter one skein 
in each, work cold 10 minutes, wash, and dry. 

(a) 1 per cent beta-naphthol 1 and 1 per cent sodium hydroxide 
in 200 cc. water. 

(b) 1 per cent resorcin and 2 per cent sodium hydroxide in 
200 cc. water. 

(e) 2 per cent toluene diamine and 4 per cent sodium car¬ 
bonate in 200 cc. water. 

Tabulate your results. 

The preceding experiment shows that different de¬ 
velopers, acting upon diazotized primuline, produce dif¬ 
ferent dyes of different colors. It also shows that light 
decomposes diazotized primuline, and prevents it from 
uniting with the developer. 

Precautions in Diazotizing. — In diazotizing primuline, 
or any other body, the solution of nitrous acid must be 

1 The solution provided contains beta-naphthol dissolved in an equal 
quantity of sodium hydroxide, 
c 


18 


PRINCIPLES OF DYEING 


cold for two reasons. First, a warm solution would have 
an injurious effect upon the process of diazotizing, either 
by preventing it from taking place, or by decomposing the 
diazonium compound formed. Many diazonium com¬ 
pounds are stable only at a low temperature, and decom¬ 
pose immediately if the temperature is only slightly ele¬ 
vated. In the second place, nitrous acid is not readily 
soluble even in cold water, and would escape rapidly if the 
temperature is elevated. 

For these two reasons, but more particularly the first, it 
is often necessary to cool the diazotizing bath by means of 
ice. Dyes which are diazotized and developed are some¬ 
times called ice colors. 

Another necessary precaution in diazotizing is that the 
bath should contain sufficient nitrous acid. Otherwise the 
primuline is diazotized only in part, and inferior colors 
result. 

Developers.—The developers used for primuline are 
organic compounds, either amines, or phenols. 

Amines are basic in nature, and unite with acids to form 
salts. Thus aniline, an amine, combines with hydrochloric 
acid to form aniline hydrochloride, a reaction resembling 
that between ammonia and the same acid. 

C 6 H 5 NH 2 + HC 1 = C 6 H 5 NH 3 C 1 . 

NH 3 + HC 1 = NH 4 C 1 . 

Phenols are weakly acid in nature, forming salts with 
bases. Thus phenol forms sodium phenolate : — 

C 6 H 5 OH + NaOH = C 6 H 5 ONa + H 2 0 . 

The phenol most largely used in developing such colors 
as primuline is beta-naphthol. This is a compound having 


CONGO RED — PRIMULINE 


19 


the formula C 10 H 7 OH, which is sold as a powder, or as 
lumps. It is only sparingly soluble in hot water, hardly 
soluble at all in cold water. It dissolves easily in caustic 
soda, a sodium salt, C 10 H 7 ONa, being formed. This com¬ 
pound is slowly oxidized by the air, and the solution be¬ 
comes dark colored. Other developers are : — 


Phenol. 

Resorcin. 

Alpha-naphthol . . . 

Naphthalamine ether . 

Phenylene diamine . . 

Toluene diamine 


C 6 H 5 OH 

C 6 H 4 (OH) 2 

C 10 H-OH 



“6NH 2 

C 6 H 4 (NH 2 ) 2 

c,h 6 (nh 2 ) 2 


Fastness of the Colors.—The colors produced by diazo- 
tizing and developing primuline are insoluble in water; 
hence they are fast to washing, and do not bleed. Very 
little of the color is removed even by boiling water. They 
are little affected by acids or alkalies, but are affected by 
light. 

Experiment 14. — Test the fastness of the direct dyeings and 
the diazotized and developed dyeings of primuline to boiling 
water, washing, acids, and alkalies, as described in Experiments 
6, 7, 9, and 10. 

Summary. — Primuline is an important member of a 
group of direct cotton colors which are diazotized and de¬ 
veloped to produce colors highly fast to washing. They 
resemble primuline in many particulars. 



CHAPTER III 


FUCHSINE 

Fuchsine, or magenta, was discovered in 1859, being 
one of the first artificial dyes made. One method of pre¬ 
paring it is by oxidizing a mixture of aniline and toluidine, 
which can be made from compounds found in coal tar. 
The crude product is dissolved in hot water and allowed 
to cool, when the dye crystallizes out and is separated. 
The solution, or “mother liquor,” as it is called, which 
contains some of the dye mixed with other substances, is 
evaporated and less pure grades of fuchsine are obtained, 
which are sold under various names, such as cerise, grena¬ 
dine, amaranth, etc. 

Composition. — Fuchsine, like almost all dyes in general 
use, comes into commerce in varying degrees of purity. 
When pure, it consists of a mixture of the hydrochloric 
acid salts of two bases, para-rosaniline, and rosaniline; 
rosaniline is present in greater quantities, and, for the 
sake of clearness, we shall speak of fuchsine as if it con¬ 
tained rosaniline only. 

Properties. — Fuchsine appears as a powder, or as crys¬ 
talline masses, with a brilliant green metallic luster. It is 
soluble in 250 parts water, much more readily in alcohol. 
It dissolves in concentrated sulphuric acid with a brownish 
yellow color; the solution becomes nearly colorless on 
dilution with water. 


20 


FUCHSINE 


21 


Sodium or potassium hydroxide added to a solution of 
fuchsine precipitates a mixture of the two bases, para- 
rosaniline and rosaniline, as a reddish brown precipitate. 
With a weak solution of fuchsine, no precipitate appears; 
the solution becomes colorless. 

C 20 H 20 N 3 C 1 + NaOH = C 20 H 20 N 3 OH + NaCl; 

Rosaniline base. 

or, condensed: — 

BC 1 + NaOH = BOH + NaCl. 

When strong hydrochloric or sulphuric acid is added to 
a solution of fuchsine, it changes color, becoming orange- 
yellow to colorless, according to the strength of the solu¬ 
tion. If the solution is heated, it again becomes pink. 
The first change is due to the formation of acid salts of 
rosaniline, which are orange-yellow, as for example: — 

C 20 H 20 N 3 C 1 T 2 HC 1 = C 20 H 20 N 3 C 1 .2 HC 1 \ 

Fuchsine. Acid salt. 

or, abbreviated: — 

BC 1 + 2 HC 1 = BC 1 . 2 HC 1 . 

The acid salt is decomposed into fuchsine and acid 
when it is heated, or diluted with water. A great many 
dyes behave in the same way, forming acid salts which are 
different in color from the basic salts, and are easily de¬ 
composed. Acetic acid does not, as a rule, produce such 
salts. 

Leuco Compounds. — If we heat a solution of fuchsine 
with zinc and acetic acid, the solution is decolorized. 
Congo red behaves in the same way. In the case of fuch¬ 
sine the nascent hydrogen combines with the color, form¬ 
ing leuco-rosaniline hydrochloride, which is colorless. 


22 


PRINCIPLES OF DYEING 


C 20 H 20 N 3 C1 + 2 H = C 20 H 21 N 3 HC1; 

Fuchsine. Leuco-rosaniline hydrochloride. 

or, condensed: — 

BC1+ 2 H = HjjBCl. 

When this colorless compound is brought in contact with 
oxidizing agents, such as chromic acid, it loses hydrogen 
and is again converted into fuchsine. 

C 20 H 21 N 3 HC1 + O = C 20 H 20 N 3 C1 + H 2 0 ; 

or, abbreviated: — 

h 2 bci + o = bci + h 2 o. 

Leuco-rosaniline is also oxidized very slowly by the air. 

A colorless body which is formed from a colored com¬ 
pound by the addition of hydrogen to its molecule, and 
which loses its hydrogen by oxidation, forming the origi¬ 
nal colored body, is called a leuco compound, the word 
“ leuco ” meaning white or colorless. 

Many dyes are reduced, like fuchsine, to leuco bodies; 
on the other hand, others, like Congo, are broken up by 
reducing agents, and the product cannot be oxidized back 
to the original coloring matter. This property is an aid in 
the identification of dyestuffs. 

Experiment 15. — Examine some fuchsine and describe its 
appearance. Dissolve a little in concentrated sulphuric acid and 
note the color. Pour the solution into water (color). 

Dissolve a little of the dyestuff in hot water. Add hydrochlo¬ 
ric acid to a portion of the solution, and allow it to stand fif¬ 
teen minutes. Explain what happens. Heat the acid solution. 
Explain. 

To another part of the solution, add sodium hydroxide and 
heat gently. Explain. Write condensed reactions. 


FUCHSINE 


23 


Add zinc dust and acetic acid (see Exp. 3) to a portion of the 
solution, and heat it to boiling 10 minutes. Explain. Filter the 
solution and saturate a filter paper with it. Touch the paper with 
a glass rod moistened with a solution of chromic acid, and observe 
it after several hours. What happens? 

Rosaniline Tannate.— Rosaniline and tannic acid unite 
to produce a salt, or lake as it is called, which is not solu¬ 
ble in water, but is soluble in acids, such as hydrochloric 
acid, acetic acid, or an excess of tannic acid. The lake is 
formed when solutions of tannic acid and fuchsine are 
brought together: — 

2 C20H20N3CI + H 2 C 14 H s 0 9 = (C 20 H 20 N 3 ) 2 C 14 H 8 O 9 + 2 HC 1 . 

Fuchsine. Tannic acid. Rosaniline tannate. 

In the condensed form, the reaction is written : — 

2 BC 1 + H 2 Ac = B 2 Ac + 2 HC 1 . 

Experiment 16. — Add a few drops of a solution of tannic acid 
to a solution of fuchsine, and heat gently. What happens? Di¬ 
vide the solution into two portions; to one add an excess of tan¬ 
nic acid, and to the other add hydrochloric acid. What happens? 

Other Salts. — Fuchsine sometimes occurs in commerce 
as rosaniline acetate, sulphate, or nitrate. Other salts 
may be prepared. 

Fuchsine combines with some direct cotton colors, like 
Congo, to form insoluble salts, or lakes: — 

BC 1 + AcNa = BAc + NaCl. 

Action toward Fibers. — Fuchsine is a direct dye for 
wool, but not for cotton. Wool takes it up readily, and 
exhausts the bath. Cotton is indeed stained when boiled 
with fuchsine, but the color is rapidly removed by washing. 


24 


PRINCIPLES OF DYEING 


Experiment 17. — Dye a 5-gram skein of wool in 1 per 
cent fuchsine in 200 cc. water. Heat to boiling 30 minutes, 
remove, wash, and dry. Is the bath exhausted? 

Dye a 10-gram skein of cotton in the same way, but dry 
without washing. Then wash a portion of the skein with 
water. 

Test the fastness of fuchsine on wool to washing (Exp. 7), 
acids (Exp. 9), and alkalies (Exp. 10). 

Dyeing Cotton with Fuchsine. — Fuchsine is sometimes 
applied to cotton for the production of light tints by work¬ 
ing the fiber in a hot solution of the dye, and drying it 
without washing. The bath is not exhausted, and the color 
is easily removed by washing. This method may be called 
dyeing by saturation , as the material is simply dried while 
saturated with a solution of the dye for which it has 
no affinity. 

Another method, seldom used, is to animalize the fiber, 
i.e. give it the properties of an animal fiber. The cotton 
is saturated with a solution of albumen (from eggs or 
blood), and passed through hot water, which coagulates 
the albumen and renders it insoluble. The coating of 
albumen on the surface of the fiber has an affinity for fuch¬ 
sine, and similar dyes, and withdraws it from solution, ex¬ 
hausting the bath. 

The chief methods for dyeing cotton with fuchsine are 
to produce an insoluble tannate of the color on the fiber, 
or to form insoluble salts with the color acids of direct 
cotton colors. 

Mordants. — Cotton absorbs tannic acid from solution, 
and when afterwards brought in contact with fuchsine, 
withdraws the dye from solution, and is dyed. The dyeing 


FUCHSINE 


25 


is due to the affinity of the tannic acid for the dyestuff, not 
to direct absorption by the fiber. Rosaniline tannate is 
produced in an insoluble form within the fiber. A sub¬ 
stance which, like tannic acid, unites with a dye to fix it 
upon a fiber, is called a mordant. The compound of dye 
and mordant is a lake. 

Turkey-red oil is another mordant used sometimes to fix 
basic dyes upon cotton. It is a mixture of fatty acids pre¬ 
pared by treating castor oil with sulphuric acid. 

Direct cotton colors may serve as mordants for fuchsine 
and similar colors. 

Fixing Tannic Acid. — When tannic acid acts upon fuch¬ 
sine, there is always a liberation of hydrochloric acid, 
which prevents the reaction from being complete, as the 
lake is soluble in acid : — 

2 BC 1 + H 2 Ac = B 2 Ac + 2 HC 1 . 

Insoluble metallic tannates possess an attraction for fuch¬ 
sine equal to tannic acid, if not greater. The presence of 
the metal aids in the decomposition by reason of a portion 
neutralizing the liberated acid of the coloring matter, and 
it is probable that a very insoluble tannate of the metal 
and color base is produced. The process of converting 
tannic acid into insoluble metallic salts is termed fixing , 
and is usually carried out after mordanting with tannic 
acid. Salts of antimony, iron, and sometimes tin are used 
as fixing agents. 

Antimony tannate is colorless, and gives the brightest 
and fastest colors. It is produced by treating the goods 
mordanted with tannic acid with a solution of antimony 1 


26 


PRINCIPLES OF DYEING 


potassium tartrate (tartar emetic) or other antimony salts. 
The reaction is as follows : — 

2 KSb0C 4 H 4 0 6 +H 2 C 14 H 8 0 9 = 

Tartar emetic. Tannic acid. 

2 KHC 4 H 4 0 6 +(Sb0) 2 C 14 H 8 0 9 . 

Potassium Antimony tannate. 

acid tartrate. 

The bath becomes acid from the formation of potas¬ 
sium acid tartrate, which, after a time, prevents the 
reaction from going further. It can be neutralized with 
soda. 

Iron tannate is dark in color, being the basis of most 
black inks. It is produced by the action of ferrous sul¬ 
phate or other iron salts upon tannic acid : — 

FeS0 4 + H 2 C 14 H 8 0 9 = FeC 14 H 8 0 9 + H 2 S0 4 . 

The ferrous tannate is oxidized by the air. 

The reaction does not go far unless the sulphuric acid is 
from time to time neutralized with sodium carbonate. Or 
the acid is neutralized as fast as it forms if chalk is added 
to the bath. Iron tannate can be used only in fixing tannic 
acid for very dark colors. 

Experiment i8. — Boil three io-gram skeins of cotton yarn with 
5 per cent tannic acid dissolved in 500 cc. water, until the cotton 
is thoroughly wetted out, at least 15 minutes. Allow the solution 
to cool an hour, working the yarn from time to time. Tannic acid 
is absorbed more readily by cotton from a cold solution. Squeeze 
well, and proceed as below : — 

Skein No. 1. Dye as directed below. 

Skein No. 2. Fix with antimony, by working 10 minutes in a 
bath of 2 per cent tartar emetic in 200 cc. water. What is formed? 
Wash well, and dye as directed below. 


FUCHSINE 


27 


Skein No. 3. Fix with iron, by working 10 minutes in a bath of 
5 per cent copperas and 3 per cent calcium carbonate in 200 cc. 
water. What is formed? Wash well and dye. 

Prepare three dye-baths, each with 1 per cent fuchsine in 200 cc. 
water. Enter a skein in each bath, raise the temperature to 65° 
C., and keep at this temperature 20 minutes. The yarn should 
be worked carefully. Squeeze, and dry without washing. 

How do the three skeins differ in color? Test fastness to wash¬ 
ing, acids, and alkalies as directed in Experiments 7, 8, and 9. 
How do they differ in fastness ? 

Action of Hard Water.—The action of hard water in 
dyeing with fuchsine is illustrated by the following experi¬ 
ment : — 

Experiment 19. — Prepare a dye-bath with 1 per cent fuchsine 
and 50 cc. lime-water in 200 cc. water, and dye a 5-gram skein 
of wool as directed in Experiment 17. Dye another skein in the 
same way, leaving out the lime-water. What is the difference ? 

Lime-water or hard water with temporary hardness 
precipitates fuchsine from solution as the free color base, 
and prevents a portion of it from going on the wool. The 
precipitate is liable to settle on the material and cause 
dark spots ( dye-spots ), which are difficult to remove. 

The action of hard water on Congo is due to the precipi¬ 
tation of the dyestuff in the form of an insoluble calcium 
salt; with fuchsine, the alkalinity of the water precipitates 
the insoluble color base. The causes and the remedies are 
different. In the case of Congo, the hard water can be 
purified only by removal of calcium salts; in the case of 
fuchsine, the alkalinity of the water may be neutralized 
with an acid. 

Printing Fuchsine. — Advantage is taken of the solu¬ 
bility of rosaniline tannates (and the tannates of similar 


28 


PRINCIPLES OF DYEING 


colors), in acetic acid, in printing cotton cloth. The cloth 
is printed with a mixture of the dyestuff, tannic acid, 
acetic acid, and suitable thickening agents, and steamed. 
Acetic acid is driven off, and the tannate is fixed in an 
insoluble form. The cloth is then passed through a solu¬ 
tion of tartar emetic, which completes the fixation. 

Basic Colors. — Fuchsine is a representative of an impor¬ 
tant class of dyestuffs known as basic colors. They are all 
salts of color bases, direct dyes for wool but not for cotton, 
and are dyed on cotton with a tannic acid mordant, or 
other mordants of acid nature. Hard water has the effect 
of precipitating them as the free color base. 


CHAPTER IV 


BIEBRICH SCARLET-ALKALI BLUE 

Biebrich scarlet is a scarlet dye. It is also called scarlet 
B, scarlet 3 RB or ponceau 3 RB, new red L, and imperial 
scarlet. The letters after the name of a dye sometimes 
indicate some particular brand or strength of color, some¬ 
times indicate the hue of the dye. Thus, methyl violet B 
is a bluer shade than methyl violet R. The letters used 
are B for blue, R for red, G for yellow (German, gelb), 
or sometimes J (French, jaiine), and V for violet. 

Properties. — Biebrich scarlet occurs as a brown-red 
powder, easily soluble in water, forming an orange-red 
solution. It dissolves with a green color in concentrated 
* sulphuric acid; diluted with water, the color changes from 
blue to red, and a red-brown precipitate separates. 

Like congo and primuline, Biebrich scarlet is the sodium 
salt of a color acid. Hydrochloric acid precipitates the 
free color acid from solution in the form of a flocculent, 
dark red precipitate, unless the solution is very dilute: — 

Na 2 Ac + 2 HC1 = H 2 Ac + 2 NaCl. 

Biebrich scarlet. Color acid. 

The aluminium and calcium salts are not soluble, and 
are precipitated when solutions of the dye and of calcium 
or aluminium salts are brought together. 


29 


30 


PRINCIPLES OF DYEING 


Zinc dust and acetic acid reduce the dye to colorless 
bodies; a leuco compound is not formed. 

Action toward Fibers. — Biebrich scarlet is a direct dye 
for silk and wool. It colors cotton to a certain extent, but 
the color washes out very readily with water. Silk and 
wool are dyed with Biebrich scarlet in an acid bath; in a 
neutral bath the dyeings are less bright, and the bath is 
not exhausted. 

Experiment 20. — Dye a 5-gram skein of wool in a bath of 2 per 
cent Biebrich scarlet in 200 cc. water, boiling 15 minutes. Re¬ 
move, rinse, and dry. 

Dye another skein as directed above, with the addition of 2 per 
cent sulphuric acid. Compare the two skeins and the two dye- 
baths. What is the effect of the acid ? 

Action of the Acid.—The acid has a twofold action: 
in the first place, it liberates the color acid of the dye, 
which has a much greater affinity for wool than has its 
salts. In the second place, the acid acts chemically upon 
the wool, increasing its power to take up dye. Part of 
the acid is withdrawn from solution to enter into combina¬ 
tion with the wool. 

Experiment 21. — Boil a 5-gram skein of wool for 15 minutes in 
a bath of 10 per cent sulphuric acid in 200 cc. water. Wash 
thoroughly, and dye with 2 per cent Biebrich scarlet in 200 cc. 
water. Is the bath exhausted? Compare with the colors ob¬ 
tained in Experiment 20. 

Dye a second skein with 2 per cent Biebrich scarlet and 0.3 per 
cent sulphuric acid in 200 cc. water. This quantity of acid is 
sufficient to liberate the free color acid. Is the bath exhausted? 

Wool boiled with sulphuric acid can be dyed with Bie¬ 
brich scarlet without any addition of acid to the bath, 


BIEBRICH SCARLET —ALKALI BLUE 


31 


while if the acid added to the dye-bath is only in suffi¬ 
cient quantity to liberate the color acid, the wool is not 
dyed a full shade. In practice, about ten times as much 
acid is used as is needed to liberate the free color acid. 

Assistants. — Sulphuric acid, sodium sulphate, sodium 
chloride, and other substances which aid in dyeing with¬ 
out actually entering into combination with the dyestuff to 
form a color lake, are termed assistants. 

Stripping Biebrich Scarlet. — The dye is removed from 
wool by boiling it with a solution of ammonia, sodium car¬ 
bonate, or ammonium acetate. Ammonium acetate or 
ammonia is preferred to sodium carbonate, which is liable 
to injure the fiber. 

Experiment 22. — Boil half of a wool skein dyed with Biebrich 
scarlet with 2 per cent ammonium acetate in 100 cc. of water for 
half an hour. Is the color removed ? 

Dyeing Cotton. — Biebrich scarlet cannot be fixed upon 
cotton fast to washing. It is used to a considerable extent 
on account of its fastness to light in cases where fastness 
to water is not necessary. Cotton is dyed in several ways, 
of which the following may serve as examples: — 

(a) Dyeing by saturation. The cotton is worked in a 
bath containing the dye and some salts, and dried without 
washing. 

( b ) Dyeing as aluminium salt. The cotton is boiled 
with a solution of the dye to which alum has been added. 
The dye is taken up in the form of an aluminium salt, 
which is less soluble in water than its sodium salt, and has 
greater affinity for the fiber. Darker colors are produced 
than by method (a). 


32 


PRINCIPLES OF DYEING 


(c) Dyeing on aluminium mordant. The cotton is worked 
in a solution of basic aluminium sulphate, formed by add¬ 
ing sodium carbonate to alum : — 

4 KA1(S0 4 ) 2 + 3 Na 2 C0 3 -b 3 H 2 0 = Al 4 (S0 4 ) 3 (OH) 6 
-f- 3 Na 2 S0 4 + 3 C0 2 + 2 K 2 S0 4 . 

The cotton decomposes this body, and absorbs it in the 
form of a still more basic salt. It is then worked in the 
dye-bath, when the dye is fixed in the form of its alumin¬ 
ium salt. 

{d) Dyeing on tin mordant. The cotton is worked in 
sodium stannate, Na 2 Sn0 3 , and then in basic aluminium 
sulphate. Stannic hydroxide and aluminium hydroxide 
are formed. The cotton is then dyed. In no case is the 
bath exhausted. 

Experiment 23. — Dye skeins of boiled-off cotton yarn with 
Biebrich scarlet as follows and dry without washing : — 

No. 1. Dye with 2 per cent Biebrich scarlet and 20 per cent 
salt in 200 cc. water, boiling 15 minutes. 

No. 2. Dye with 2 per cent Biebrich scarlet, 20 per cent salt, 
and 25 per cent alum in 200 cc. water, boiling 15 minutes. 

No. 3. Mordant by working carefully, in a bath of 10 per cent 
alum and 2 per cent sodium carbonate in 200 cc. water. 
(Reaction.) Wring out and dye, without washing, in a bath of 
2 per cent Biebrich scarlet and 20 per cent salt in 200 cc. water. 
Enter the skein at 50° C., and work 15 minutes without further 
heating. 

No. 4. Work 15 minutes in a bath of 5 per cent sodium stan¬ 
nate in 200 cc. water. Squeeze, and work 15 minutes in 5 per 
cent alum and 1 per cent sodium carbonate in 200 cc. water. 
Wring out, and dye as with skein No. 3. 

How do these skeins differ in color? Test fastness to washing 
(Exp. 7). How do they compare? 


BIEBRICH SCARLET —ALKALI BLUE 


33 


Hard Water. — Biebrich scarlet is precipitated by hard 
water from neutral solutions, but not from acid solutions. 
Hence hard water interferes with the dyeing of cotton, 
but not with wool dyeing. 

Alkali Blues. — The alkali blues, also called Nicholson’s 
blue, and soluble aniline blue, are prepared by the action 
of sulphuric acid upon aniline blue, a basic color which is 
insoluble in water, but soluble in alcohol. 

Composition. — The aniline blues, like fuchsine, are mix¬ 
tures of several chemical compounds. There are several 
varieties, differing in color and composition. The brands 
are indicated by letters according to their shades. Thus 
we have alkali blue 6 B to 4 R, ranging from a greenish 
blue, the most valuable, to a red blue, or purple. 

Properties. — The alkali blues appear as blue powders, 
4 R being of a reddish cast. They are sparingly soluble in 
cold water, freely soluble in hot water. They dissolve in 
concentrated sulphuric acid to a red-brown solution; on 
diluting, a blue precipitate appears. 

With sodium hydroxide, the solution becomes claret red. 

With zinc and acetic acid, the corresponding leuco com¬ 
pound is formed. 

Like congo and Biebrich scarlet, the alkali blues are 
salts of a color acid; the free color acid is precipitated 
when hydrochloric or sulphuric acid is added to a solution 
of the dye. 

Alkali blue is precipitated by hard water. 

Action toward Cotton and Wool. —The alkali blues are 
acid colors, and consequently cannot be dyed on cotton 


D 


34 


PRINCIPLES OF DYEING 


fast to washing. The methods for dyeing on cotton are 
the same as for Biebrich scarlet. 

Alkali blue is removed from acid, alkaline, or neutral 
solutions by wool or other animal fibers, though, unless the 
bath is acid, it is not exhausted. On account of the fact 
that the color acid is nearly insoluble in water, wool and 
silk are always dyed with alkali blue in a bath made 
alkaline with borax. The color acid is liberated, and the 
proper color developed subsequently by a treatment with 
dilute sulphuric acid. The lower the temperature of the de¬ 
veloping bath, the greener is the shade of blue obtained; if 
the temperature is raised, the shades become redder in tone. 

Experiment 24. — Examine alkali blue. Dissolve some in 
water, and try the effect of sodium hydroxide and hydrochloric 
acid upon it. 

Dye a 5-gram skein of woolen yarn in a bath of \ per cent 
alkali blue 4 B and 2 per cent borax in 200 cc. water, boiling 
half an hour. Remove a sample for your scrap-book, and develop 
the remainder by working for a few minutes at 6o° C. in a bath 
of 2 per cent sulphuric acid in 200 cc. water. 

Dye another skein as directed above, with alkali blue 4 R, and 
develop with sulphuric acid at 8o° C. 

Test fastness of the developed colors to acids, alkalies, and 
washing (Exps. 7, 9, and 10). What is the effect of developing? 
What is the difference between the 6 B and the 4 R ? 

Acid Colors. — Biebrich scarlet and alkali blue are acid 
dyes. Congo and fuchsine are dyed in the form of salts, 
but Biebrich scarlet, alkali blue, and all other acid colors 
are dyed upon wool in the form of the color acid. They 
are dyed from an acid bath, or an alkaline bath, and in the 
latter case require an after treatment with acid to liberate 
the color acid and develop the color. 


CHAPTER V 


LOGWOOD 

Logwood, or Campeachy wood, is the wood of a large 
free which grows abundantly in the West Indies, Mexico, 
and parts of Central America. Logwood was introduced 
as a dye soon after the discovery of America. 

Preparation. — Logwood is imported in logs weighing 
about 400 pounds. The fresh wood is colorless, or nearly 
so, and contains a glucoside, composed of haematoxylin 
and sugar. It is cut into chips or rasped, and aged, i.e. 
placed in heaps to ferment, an operation which requires 
great care. The glucoside is decomposed, liberating 
haematoxylin, and at the same time a large part of the 
haematoxylin is oxidized in the air to haematin, the active 
coloring principle. When sufficiently aged, the wood is 
ready for use. 

Logwood extracts are prepared by extracting the wood 
with hot water and evaporating the solution under reduced 
pressure at a temperature not too high. The wood is ex¬ 
tracted a second and a third time, yielding inferior grades 
of extract. 

Composition.—The wood contains woody fiber, water, 
mineral matter, haematin, haematoxylin, and other sub¬ 
stances. It varies in composition. 


35 


36 


PRINCIPLES OF DYEING 


The extracts contain haematin and haematoxylin in an 
impure form. They are sometimes adulterated with glu¬ 
cose, molasses, chestnut extract, and other substances. 

Properties. — Logwood chips or raspings appear as red, 
woody substances. The extract is a thick liquid, or paste. 
A decoction of logwood, or a solution of the extract, has a 
color ranging from orange-yellow to a dark reddish brown, 
according to the strength of the solution. The color is 
removed by zinc and acetic acid. 

Salts. — Both haematin and haematoxylin are acids, and 
form salts with bases. The reactions of a decoction of 
logwood are due to the simultaneous presence of both 
haematin and haematoxylin. 

The salts of lead, iron, copper, tin, silver, and some others 
with haematin are not soluble in water, and are precipi¬ 
tated as colored precipitates when any salts of these 
metals, in solution, are added to a solution of logwood. 

Action to Fibers. — Logwood as a direct dye produces a 
reddish brown color of no practical value. 

Experiment 25. — Boil a cotton skein with 30 per cent logwood 
extract in 200 cc. water for half an hour. Squeeze, remove a 
sample for your scrap-book, and save the dye-bath and remainder 
of yarn for Experiments 26 and 27. 

Treat a skein of wool in the same way, using 10 per cent log¬ 
wood extract. 

Which skein is colored darker? Is either dye-bath exhausted? 

Combined with iron, aluminium, chromium, or copper, 
logwood produces valuable dyes of different colors. That 
is to say, it requires metallic mordants. 


LOGWOOD 


37 


Experiment 26.— (a) Work the cotton skein obtained in the 
preceding experiment 10 minutes in a cold bath of 7 per cent 
potassium bichromate and 5 per cent copper sulphate in 200 cc. 
water. The color produced is due to the oxidation of the haema- 
toxylin to haematin by potassium bichromate, and combination of 
haematin with the metals to form a mixture of copper and chro¬ 
mium haematates. 

( b ) Boil the wool obtained in Experiment 25 with 5 per cent 
ferrous sulphate and 1 per cent copper sulphate in 200 cc. water 
for half an hour. In this case copper haematate and ferrous haema- 
tate are formed, and the latter is probably oxidized to ferric 
haematate by the air. 

Wool has enough affinity for the coloring principle of 
logwood to absorb sufficient of it to produce a good color 
when afterward mordanted. Cotton, even from the strong 
solution used, absorbs only enough logwood to fix the mor¬ 
dant ; for a good color, a second dyeing is necessary. 

Experiment 27. — Boil the cotton mordanted in Experiment 26 
with the dye-bath saved from Experiment 25. A good black is 
produced. Test fastness to washing. 

Behavior of Fibers to Mordants.—Two classes of mor¬ 
dants are used in dyeing: — 

( 1 ) Acid mordants , such as tannic acid, or Turkey-red 
oil, which are used to fix fuchsine and other basic dyes on 
cotton in the form of insoluble tannates, etc. 

( 2 ) Basic or metallic mordants , which combine with dyes 
like logwood with acid properties to form highly colored 
lakes of iron, aluminium, etc. 

The metallic mordants behave differently toward cotton 
or linen and wool or silk. 

To mordant wool with metallic mordants it is boiled 
with solutions of alum, or potassium bichromate, with the 


38 


PRINCIPLES OF DYEING 


addition of acids, whose function will be discussed later. 
The wool acts chemically upon the salts, decomposes them, 
and fixes the aluminium or chromium so that it cannot be 
washed out, and in such a form that it combines readily 
with logwood and similar colors to form the desired lakes. 

Experiment 28. — Mordant a 5-gram skein of wool by boiling 
half an hour in a solution of 5 per cent alum and 3 per cent oxalic 
acid in 200 cc. water. Dye by boiling half an hour with 3 per 
cent hsematin in 200 cc. water. Remove and wash. Is the bath 
exhausted? Test fastness to washing. 

The wool fixes the alum in the form of a basic salt, leav¬ 
ing part of the acid in solution; it is afterward dyed blue 
by combination of the aluminium with the coloring princi¬ 
ple of logwood. 

Cotton is chemically less active than wool, and cannot 
decompose salts such as alum. It can decompose basic 
salts and fix them feebly. 

Experiment 29. — Prepare a mordanting bath of basic alumin¬ 
ium sulphate (see Exp. 23) by dissolving 10 per cent alum and 2 
per cent sodium carbonate in 200 cc. water, and work a boiled-off 
cotton skein in the solution 15 minutes. Wring out and dye with¬ 
out washing as described in Experiment 28. 

The method illustrated by Experiment 29 is of no prac¬ 
tical value for dyeing with logwood. Metallic mordants 
are fixed upon cotton by the production of insoluble 
compounds. Two methods of fixing iron for logwood 
dyeing are illustrated by Experiments 30 and 31. 

Experiment 30. — Work a boiled-off skein of cotton yarn 10 
minutes in a solution of 50 per cent ferric sulphate in 100 cc. 
water. Squeeze well, and pass through lime-water, which precipi¬ 
tates ferric hydroxide : — 

Fe 2 (S0 4 ) 3 + 3 Ca(OH) 2 = 2 Fe(OH) 3 + 3 CaS0 4 . 


LOGWOOD 


39 


Dye with io per cent logwood extract in 200 cc. water, boiling half 
an hour. The cotton is dyed black. 

Experiment 31. — Boil two 10-gram skeins of cotton yarn with 
10 per cent sumac extract (which contains tannic acid) in 200 cc. 
water, until thoroughly wetted out, and allow to stand in the solu¬ 
tion over night. Then squeeze and work 15 minutes in a bath of 
15 per cent ferric sulphate in 200 cc. water ; iron tannate is formed. 
Squeeze and work 10 minutes in 100 cc. lime-water. The excess 
of iron salt on the fiber is decomposed with the production of 
ferric hydroxide. Wash well, remove a sample, and dye with 10 
per cent logwood extract in 200 cc. water, boiling half an hour. 
Remove and wash. One skein is saved for Experiment 34. 

In the first case, the fiber is saturated with a strong 
solution of a ferric salt, and the salt dissolved in the water 
adhering to the fiber is decomposed with lime-water. 

In the second case, the metallic mordant is fixed by 
means of tannic acid, which has some affinity for cotton, 
and also unites with the metal. 

In both cases the cotton is dyed black by the logwood. 

Polygenetic Colors. — The color produced by logwood 
depends upon the mordant used with it and the way in 
which it is applied. With aluminium (Exps. 28 and 29) 
the color is blue; with iron (Exps. 30 and 31), black; with 
potassium bichromate and oxalic acid, a shade of blue; 
with potassium bichromate and sulphuric acid, black. 

Experiment 32. — Mordant a 5-gram skein of woolen yarn 
with 3 per cent sodium bichromate and 2 per cent oxalic acid in 
200 cc. water, boiling half an hour. Remove a sample and boil the 
remainder half an hour with 3 per cent haematin in 200 cc. water. 

Mordant a second skein as directed above with 3 per cent so¬ 
dium bichromate and i\ per cent sulphuric acid. Remove a 
sample and dye with 7 per cent haematin. 


40 


PRINCIPLES OF DYEING 


Dyestuffs from which more than one color can be pro¬ 
duced by the use of different mordants, are called polyge- 
netic colors. Monogenetic colors are those which yield only 
one color, or shade of that color, no matter what mordant 
may be used. 

Assistants for Metallic Mordants. — Different results 
were obtained in the preceding experiment, according as 
sulphuric acid or oxalic acid were used as assistants with 
potassium bichromate. The results are explained as 
follows: — 

(1) Sulphuric acid liberates chromic acid from the 
potassium bichromate, which is taken up by the fiber: — 

K 2 Cr 2 0 7 -f- H 2 S 0 4 = k 2 S 0 4 T 2 Cr 0 3 T H 2 0 . 

The chromic acid is partly reduced by the wool fiber; 
the unreduced chromic acid oxidizes the coloring principle 
of logwood and then combines with it to form a black 
lake. 

(2) Oxalic acid slowly produces chromium hydroxide, 
which is taken up by the fiber: — 

3 H 2 C 2 0 4 + 2 K 2 Cr 2 0 7 = 2 K 2 Cr 0 4 + 2 Cr(OH) 3 -f 6 C 0 2 . 

The chromium hydroxide combines directly with the log¬ 
wood without oxidation. Cream of tartar (potassium bitar¬ 
trate) and lactic acid, which are also used, have the same 
effect as oxalic acid. Besides influencing the composition 
of the body absorbed by the wool, assistants are used with 
metallic mordants for the following purposes : — 

(1) To prevent superficial and uneven mordanting. For 
example, wool decomposes alum so rapidly that, in mor¬ 
danting in large quantities, where portions of the material 


LOGWOOD 


41 


are more exposed for a time to the action of the mordanting 
liquid than other portions, some parts of the wool will take 
up the aluminium more rapidly than others, and stripes or 
spots will appear when dyeing. Further, the mordant is 
liable to be superficially attached to the wool, and the color 
lake subsequently formed will rub off. The addition of 
sulphuric acid, oxalic acid, or potassium bitartrate to the 
mordant bath prevents the alum from decomposing so 
rapidly, and aids to produce even and fast colors. 

(2) To cause more of the mordant to be taken up. Sul¬ 
phuric acid added to potassium bichromate, by liberating 
chromic acid, causes the wool to combine with a larger por¬ 
tion of the mordant. Wool takes up chromic acid from 
potassium bichromate to a certain extent: — 

K 2 Cr 2 0 7 = K 2 Cr 0 4 4- Cr 0 3 . 

It has little action upon potassium chromate. 

Methods for Dyeing with Logwood. — The methods used 
for dyeing with logwood and other mordant colors are as 
follows : — 

(1) Dyeing and mordanting (see Exps. 25 and 26). This 
method is used on wool to a certain extent, hardly ever 
on cotton. 

(2) Mordanting and dyeing (see Exps. 28, 29, 30, 31, and 
32). The usual method for dyeing with mordant colors. 

(3) Single-bath method . Dye and mordant are applied 
in the same bath. The color lake is formed and slowly ab¬ 
sorbed after the manner of a direct dye. The method has 
two disadvantages: part of the color lake is liable to be 
fixed only superficially on the fiber, and to rub off; and part 
of the dye is precipitated as a lake in the bath, and lost. 


42 


PRINCIPLES OF DYEING 


Experiment 33.— Dissolve 10 per cent logwood extract, 4 per 
cent copper sulphate, 3 per cent sodium carbonate, and 2 per cent 
ammonium chloride in 200 cc. water. Enter a 10-gram skein of 
boiled-off yarn, heat to boiling, and boil half an hour. Remove 
and wash. Test fastness to washing. 

The single-bath method is, however, largely used both 
for cotton and wool, especially in the case of cheap dyes 
like logwood, in which the cost of the dye is not great com¬ 
pared with the cost of time and labor in dyeing. 

Saddening. — Cotton or wool mordanted and then dyed 
with logwood retains an excess of the coloring matter held 
somewhat loosely. Where a high degree of fastness is re¬ 
quired, the excess is fixed or made insoluble by a second 
mordant bath. The operation is called saddening. 

Experiment 34. — Sadden one of the skeins dyed in Experiment 
31 by working 15 minutes in a bath of 1 per cent copperas in 
200 cc. water. Compare fastness of the saddened and not saddened 
skeins to washing and boiling water. 

Soaping. — The appearance of cotton dyed with logwood 
is improved by soaping. Soaping often follows dyeing, to 
remove coloring matter held only loosely by the fiber, and 
to soften the material. 

Experiment 35. — Work a skein of cotton yarn dyed black with 
logwood for 15 minutes in a solution of 4 per cent soap in 200 
cc. water heated to 6o° C. Dry without washing. 

Application of Logwood. — Large quantities of logwood 
are used for producing blacks upon cotton and wool. It is 
also used, to a slight extent, for other colors on wool. 

The color, properly dyed, possesses a high degree of fast¬ 
ness to light, washing, and acids. If not properly dyed, the 
color is liable to rub off; it is not fast to rubbing. 


LOGWOOD 


43 


Experiment 36. — Test the fastness of the dyeings obtained in 
Experiments 28, 30, 32, and 33 to washing, acids, and alkalies. 
Test fastness to rubbing of all dyeings with logwood as follows : — 
Rub vigorously on a piece of white paper or cloth. If the ma¬ 
terial is stained, the color is not fast to rubbing. 

Mordant Colors. — Logwood is a representative of the 
mordant colors. These are dyestuffs which are invariably 
fixed upon the fiber in the form of metallic lakes, with a 
color which may be different from that of the coloring 
principle. There is considerable variation in the proper¬ 
ties of the mordant colors. They are very important dyes, 
being characterized by great fastness to washing, light, and 
other agencies. 


CHAPTER VI 


INDIGO-CHROME-YELLOW 

Indigo is a valuable blue dye, which has been in use 
for ages. It is prepared from varieties of Indigofera, a 
plant of the bean family, grown chiefly in India. Indigo 
is also contained in woad, a plant formerly grown in 
Europe, but now almost entirely replaced by indigo. In 
recent years indigo has been prepared artificially. 

Preparation. — Indigo (like the coloring principle of log¬ 
wood) exists in the indigo plant and in woad in the form 
of a glucoside, indican, which is decomposed by acids into 
a sugar, and the coloring principle, indigotin. To sepa¬ 
rate indigo, the stems and leaves of the plant are covered 
with water, and allowed to ferment. The indican is de¬ 
composed and the sugar destroyed, while the indigo is 
reduced to indigo-white, and dissolves. The liquid is 
drawn off and stirred and splashed by workmen, to expose 
it to the air. The yellow liquid assumes a greenish color, 
and indigo separates in flakes. It is allowed to settle, 
and is washed several times, and finally boiled with water 
to prevent further fermentation. It is then collected and 
dried. 

Composition. —• Natural indigo, besides the blue coloring 
principle, indigo blue, or indigotin, contains small quanti¬ 
ties of other coloring matters and other impurities. Its 
composition is as follows : — 


44 


INDIGO — CHROME-YELLOW 


45 


Indigotin 
Indigo-red . 
Indigo-gluten 
Indigo-brown 
Water . . 

Ash . . 


20 to 80 per cent. 
3 to 5 per cent. 

2 to 5 per cent, 
i to 6 per cent. 

3 to 8 per cent. 

3 to io per cent. 


The average content of indigotin is 45 per cent. 

The amount of ash in inferior grades of indigo may be 
as high as 35 per cent. 

Artificial Indigo. — In 1885 A. Baeyer discovered a 
method of preparing indigo-blue, or indigotin. Other 
methods have since been devised. At present, large 
quantities of synthetic indigo are manufactured, and the 
competition between the natural and the artificial product 
is sharp. 


Properties. — Commercial indigo appears as dark blue 
cakes, sometimes as a powder. Artificial indigo is some¬ 
times sold in the form of indigo-white. Indigo is insoluble 
in water, dilute acids, or alkalies. It is soluble in boiling 
alcohol, with a blue color, but is deposited again on 
cooling. 

Nitric acid, chromic acid, and other strong oxidizing 
agents destroy indigo with the production of colorless or 
yellow bodies. Concentrated sulphuric acid dissolves it, 
forming a new dye soluble in water. 


Experiment 37. — Boil a small quantity of indigo with a little 
water in a test-tube, and filter the hot liquid. Repeat, using 
dilute hydrochloric acid. Does the indigo dissolve? 

Heat a little indigo in a test-tube with dilute nitric acid. What 
happens ? 







46 


PRINCIPLES OF DYEING 


Reduced Indigo. — Like all other dyes, indigo is reduced 
and decolorized by reducing agents. It yields a leuco 
body known as indigo-white. 

Ci6HioN 2 0 2 + 2 H = C 16 H 12 N 2 0 2 . 

Indigo. Indigo-white. 

Reduced indigo, or indigo-white from natural indigo, 
consists of the leuco compounds of indigotin with small 
quantities of reduced indigo-red. It is a grayish white 
body, insoluble in water and dilute acids, but as it has 
acid properties, it unites with bases, such as sodium hy¬ 
droxide or slaked lime, to form salts. The sodium and 
calcium salts are soluble in water. On exposure to the 
air, indigo-white is rapidly oxidized to indigotin; the 
yellowish solution becomes first green, then blue, and is 
then covered with a scum consisting of minute crystals 
of indigo. 

Dyeing with Indigo. — Indigo is applied in the form of 
the calcium or sodium salt of indigo-white, and oxidized to 
indigo by exposure to the air. The indigo is thus pro¬ 
duced in an insoluble form upon the fiber. The reduction 
of indigo is effected by several processes, which will be 
described below. The depth of color obtained with an 
indigo vat depends on : — 

(1) The strength of the solution, i.e. the quantity of 
indigo-white contained in the liquid which saturates the 
fiber. 

(2) The number of times the material is immersed in 
the liquid, or “dips,” as it is called. “One dip” indigo 
is a light color. Four dips is rarely exceeded for even 
the deepest shades. 


INDIGO — CHROME-YELLOW 


47 


The methods of reducing indigo are four, as follows: — 

(1) Copperas Vat .— The reducing agent is ferrous hy¬ 
droxide. The vat consists of a mixture of copperas 
(ferrous sulphate), slaked lime, indigo, and water. 

The copperas and slaked lime react as follows: — 

FeS 0 4 + Ca(OH) 2 = Fe(OH) 2 + CaS 0 4 . 

The ferrous hydroxide then reduces the indigo : — 

2 Fe(OH) 2 + 2 H 2 0 + 1 = 2 Fe(OH) 3 + IH 2 . 

The indigo-white dissolves in the excess of slaked lime, 
and the ferric hydroxide settles to the bottom of the vat. 
It is likely to contain some indigo, which can be recovered 
by dissolving the sediment in an acid when the vat is 
let off. 

The copperas vat is used for cotton only. 

Experiment 38. — Grind 3 g. indigo to a thin paste with a little 
water, and dilute to 500 cc. Add 8 g. copperas, and when dis¬ 
solved place the liquid in a tall beaker or cylinder. Then add 
10 g. lime, slaked, and ground to a paste with a little water. 
Allow the precipitate to settle. Saturate a boiled-off skein of 
cotton yarn in the liquid by turning it beneath the surface of the 
liquid for a few minutes. Take it out and observe any change in 
color. Give another skein of yarn three dips, exposing it to the 
air between each dip. 

(2) Hyposulphite or Hydrosulphite Vat. — In this vat the 
reducing agent is sodium acid hyposulphite (NaHS 0 2 ). 

The first step is the preparation of sodium hyposulphite, 
by the action of zinc dust in a strong solution of sodium 
acid sulphite: — 

3 NaHSOg + Zn = NaHS 0 2 + ZnNa 2 (S 0 3 \+ H 2 0 . 


48 


PRINCIPLES OF DYEING 


Zinc-sodium sulphite crystallizes from the warm solution. 

This solution is poured into a warm mixture of water, 
indigo ground to an impalpable paste, and slaked lime. 
Reduced indigo is formed, which dissolves in the calcium 
hydroxide: — 

NaHS 0 2 + I + H 2 0 = NaHS 0 3 + IH 2 . 

The hyposulphite vat does not take long to prepare. It 
is used for cotton and wool. 

Sodium acid hyposulphite is very unstable; in the air it 
oxidizes rapidly to sodium sulphite, and in closed vessels 
it changes to sodium thiosulphate : — 

2 NaHS 0 2 = Na 2 S 2 0 3 4- H 2 0 . 

Acid sodium hyposulphite. Sodium thiosulphate. 

For this reason the substance is prepared only when it is 
to be used at once. 

(3) Zinc Vat .—The vat is made up with zinc, indigo, 
water, and lime. 

Zn -J- I T 2 H 2 0 = IH 2 T Zn(OH) 2 . 

(4) The Fermentation Vat. — In this vat the indigo is 
reduced by the fermentation of bran, starch, molasses, 
or similar substances, and the indigo-white formed is 
dissolved by the addition of slaked lime. It is largely 
used in wool dyeing. 

Fastness of Indigo. — Dyeings of indigo are very fast 
to washings, acids, alkalies, and light. It is liable to rub, 
especially so when not properly applied. 

Experiment 39. — Test the fastness of the indigo dyeings 
(Exp. 38) to washing, acids, alkalies, and rubbing. 


INDIGO — CHROME-YELLOW 


49 


Indigo Extract. — Sulphuric acid dissolves indigo and 
changes it chemically. When its action is continued long 
enough, an acid is formed which is soluble in water, 
forms salts with bases, dyes wool directly in an acid bath, 
and in general has properties similar to Biebrich scarlet. 
The product is an acid dye. It is prepared in several 
degrees of purity, and is known as acid indigo extract, 
neutral extract of indigo, refined extract, best refined 
extract, and soluble indigo. Indigo extract is not appli¬ 
cable to cotton; and on wool it is not as fast to washing 
and light as indigo. 

Chrome-yellow. — Chrome-yellow is a mineral color, be¬ 
ing lead chromate (PbCr 0 4 ). It is produced by chemical 
action directly upon the fiber. Lead chromate is precipi¬ 
tated when a solution of a lead salt and a chromate or 
bichromate are brought together: — 

Pb(N 0 3 ) 2 + K 2 Cr 0 4 = PbCr 0 4 + 2 KN 0 3 . 

Lead chromate is insoluble in water; it is soluble in 
nitric acid, and is decomposed by a hot solution of sodium 
or calcium hydroxide, forming an orange compound known 
as chrome-orange : — 

2 PbCr 0 4 + Ca(OH) 2 = Pb 2 Cr 0 5 + CaCr 0 4 + H 2 0 . 

Continued action of lime-water effects complete decom¬ 
position. 

Production. — Chrome-yellow is dyed on cotton only. 
Two methods may be used : — 

(1) The cotton is impregnated with a solution of lead 
acetate or lead nitrate, and passed through lime-water to 
precipitate lead hydroxide : — 

Pb(N 0 3 ) 2 + Ca(OH) 2 = Pb(OH) 2 4- Ca(N 0 3 ) 2 . 


50 


PRINCIPLES OF DYEING 


Lead chromate is then formed by passing the material 
through a solution of potassium or sodium bichromate. 

(2) The cotton is worked in a solution of sodium plum- 
bite, prepared by the action of an excess of sodium hydrox¬ 
ide on a lead salt: — 

Pb(N 0 3 ) 2 + 4 NaOH = Na 2 Pb 0 2 + 2 NaNO s + 2 H 2 0 . 

The cotton probably absorbs lead hydroxide from this 
solution. An acidulated solution of potassium bichromate 
develops the color. Zinc sulphate may be used in place 
of the acid. 

Experiment 40. — Dissolve 2 per cent lead acetate and 16 per 
cent sodium hydroxide in 200 cc. water. Sodium plumbite 
(Na 2 PbOo) is formed. Write reaction. 

Work a skein of boiled-off cotton yarn 10 minutes in this, 
squeeze well, and work 5 minutes in a bath of 15 per cent 
potassium bichromate and 2 per cent zinc sulphate in 200 cc. 
water. Reaction? Wring, wash, and dry. Test fastness to acids, 
alkalies, washing, and rubbing. 

The baths used in this experiment are not exhausted, and are 
used continuously, being freshened up from time to time by ad¬ 
ditions of the reagents. 

Properties. — The color is very fast to light, acids, and 
washing. It adds to the weight of the cotton, sometimes 
as much as 40 per cent. Lead chromate is poisonous, and 
injurious to the health of people who handle dry yarn 
dyed with it, on account of the dust rubbed from it. 
Improperly dyed, lead chromate rubs badly. Combined 
with indigo, it produces a fast green. 

Retrospect. — We have now studied representatives of 
the different classes of dyes, namely: — 


INDIGO — CHROME-YELLOW 


51 


(1) Direct cotton colors , which are direct colors for all 
materials. They are salts of color acids, and are dyed in 
the form of salts. 

(2) Basic dyes , which are direct dyes for animal fibers, 
and are fixed on cotton by means of tannic acid. They 
are salts of color bases, and are dyed in the form of salts. 

(3) Acid dyes , which are direct dyes for animal fibers, 
and cannot be fixed firmly on cotton. They are salts of 
color acids, and are dyed in the form of acids, on wool 
and silk. 

(4) Mordant dyes , which are dyed as metallic salts of 
aluminium, chromium, etc. They are weak acids, or salts, 
and are combined with the metals on the fiber. 

(5) Insoluble dyes , which are produced in an insoluble 
form upon the fiber. 

The above division is based on practical requirements, 
and for convenience in study. There is no sharp line of 
demarcation between all the different groups; the acid 
colors and the mordant colors are frequently related to 
each other, and so are the acid colors and the direct cotton 
colors. It is sometimes difficult to say to which group a 
dyestuff belongs. 

Theory of Dyeing. — The theories of dyeing explain the 
action of direct dyes, in which the dyeing is a result of 
the attraction of fiber for dyestuff. When mordants are 
used, the force which comes into play in dyeing is the 
chemical attraction between dyestuff and mordant, which 
is largely independent of the fiber. 

Two theories have been advanced to explain the nature 
of dyeing. 


52 


PRINCIPLES OF DYEING 


(1) The mechanical theory explains dyeing as a purely 
physical process. The fibers are solid solvents, and the 
dyestuff distributes itself between dye-bath and fiber ac¬ 
cording to its solubility in the two solvents. The operation 
is analogous to the extraction of a substance from water 
by ether; such as eosine, for example. 

Experiment 41. — Dissolve a little eosine in water, and shake 
the solution in a test-tube with a little ether. The ether dissolves 
part of the eosine, and becomes colored. Add a few drops of 
hydrochloric acid, and shake again. The ether extracts nearly all 
the dye, and the water becomes almost colorless. 

(2) The chemical theory supposes dyeing to be due to 
chemical combination between dyestuff and some constitu¬ 
ents of the fiber, the resulting compound being held in a 
state of solid solution. 

The nature of dyeing really depends upon the fiber 
which is dyed. 

Cotton. — In dyeing cotton with direct cotton colors, the 
fiber probably acts as a solvent and extracts the dye from 
the bath because it is more soluble in cotton than in the 
dye liquid. When the dyed cotton is boiled with water, 
the color again distributes itself according to its relative 
solubility in the two solvents. The behavior of cotton to 
tannic acid and other mordants is explained in the 
same way. 

Wool and Silk. — In the case of the animal fibers, dye¬ 
ing is probably due to the formation of chemical com¬ 
pounds. The following facts support this statement: — 

(1) If wool is dyed with a basic color, such as fuchsine, 
the whole of the hydrochloric acid remains in solution as 
evidence of chemical action. 


INDIGO —CHROME-YELLOW 53 

(2) Wool boiled with a solution of the colorless base of 
fuchsine is dyed red, evidence of the formation of a salt. 

(3) Alcohol extracts the color from silk or wool dyed 
with night blue (a basic color), and a lake is precipitated 
on the addition of water. The lake contains the dye com¬ 
bined with an acid constituent of the fiber. Separated 
from the dye, this substance precipitates fuchsine from 
solution, as a lake which is soluble in alcohol. 

The mordanting of silk and wool seems due to chemical 
action likewise. 

Classes of Fibers. — We have seen that cotton and wool 
behave very differently towards dyes and mordants. Wool 
has a great affinity for most dyes, absorbs them readily, 
and holds them with tenacity. Wool decomposes mor¬ 
dants readily and easily, and retains them with considerable 
force. Cotton is inactive; it has little affinity for most 
dyes, and for mordants it has little attraction also. These 
differences in the behavior of wool and cotton are charac¬ 
teristic of the two classes of fibers, the animal fibers 
acting like wool, and the vegetable fibers like cotton. 


CHAPTER VII 


VEGETABLE FIBERS-COTTON 

Vegetable fibers may be divided into two groups: — 

(1) Seed hairs; that is, fibers attached to the seed of 
plants, — as the common thistle, dandelion, and cotton. 
Cotton is the only fiber of this kind of commercial im¬ 
portance. Each fiber is composed of a single cell. They 
vary from one-fourth to two inches in length. 

(2) Bast fibers ; fibers from the stem or leaves of plants, 
— as jute, flax, etc. The fibers may be quite long, in some 
cases upward of six feet. They are compound fibers, being 
composed of bundles of cells cemented together. The cells 
or ultimate fibers are quite short. 

About thirty kinds of vegetable fibers are used in the 
United States, not all of them, however, as textile fibers. 
The most important are cotton, flax (linen), hemp, jute, and 
China grass. 

Cotton. — Cotton consists of the seed hairs of various 
species of Gossypium. About two-thirds of the world’s 
supply of cotton comes from the United States. The re¬ 
mainder comes mostly from India, the East Indies, Brazil, 
and Egypt. The United States manufactures 27 per cent 
of the cotton it produces, — the Southern States one-third 
of this. 

Cotton is inclosed in a three- to five-valved capsule or 
boll , which bursts when ripe. It is picked by band, and 

54 


VEGETABLE FIBERS — COTTON 


55 


ginned to remove seeds and coarse impurities, like leaves, 
from the seed hairs or lint. The cotton is packed in bales 
weighing from three to five hundred pounds. 

The seeds are manufactured into valuable products, — 
cotton-seed oil, used as a salad oil, as a lard substitute, and 
in soap making; cotton-seed meal, used as a cattle food 
and as a fertilizer; cotton-seed hulls, used as a feed, as a 
fuel, and as a fertilizer. 

Motes. — In ginning cotton, small particles of the seeds 
are often nipped off, and pass into the lint. Sometimes 
these are not removed during the processes of cotton manu¬ 
facture, and appear on the yarn or in the woven cloth as 
black spots or motes. Under certain circumstances, motes 
give up oil to the fiber, which can cause unevenness in dye¬ 
ing, since it acts as a mordant to basic dyes. The oil may 
also prevent dye from going on to the fiber. 

Grades of Cotton. — Cotton is graded chiefly by its length 
of fiber, though its color and freedom from dust, leaves, 
seeds, and seed particles are also considered. The longer 
fibers are smaller in diameter, are silkier, and can be spun 
into finer threads than the coarser. 

Our cotton is of two types. Sea Island cotton has the 
longest and finest staple, and commands the highest price 
of any commercial cotton. It is grown only on the islands 
and along the shores of South Carolina and Florida, and to 
a limited extent along the Gulf of Mexico, and is less than 
i per cent of our crop. 

The remaining 99 per cent, known as the American Up¬ 
land, has a longer staple and is of better quality than the 
East Indian and other growths, except the Egyptian, which 


56 


PRINCIPLES OF DYEING 


comes between the American Upland and Sea Island in 
quality and price. 

Peru produces a peculiar variety of cotton, with a strong, 
rough, crinkly staple known as “vegetable wool,” much 
used by manufacturers for mixing with wool, and is diffi¬ 
cult to detect except by chemical tests. 

The following table 1 shows the average length and di¬ 
ameter in inches of the principal cotton fibers: — 



Length 

Diameter 

Sea Island. 

1.61 

.000640 

Egyptian. 

1.41 

.000655 

New Orleans. 

1.02 

.000775 

American Upland 

o-93 

.000763 

Brazilian. 

1.17 

.000790 

Indian. 

0.89 

.000844 


The diameter of other textile fibers is as follows: — 

Diameter in inches 

Silk . . . .00072 

Linen . . . .00060 to .00148 

Wool . . . .00033 to .00181 

Microscopic Appearance. — Cotton fibers, under the micro¬ 
scope, have the appearance of irregular, flattened, and some¬ 
what twisted tubes, tapering to a point at one end. They 
may be compared to a hollow twisted ribbon. The twist 
distinguishes cotton from all other fibers (Fig. 1). 

When young, each cotton fiber consists of a single circu* 

1 U. S. Dept. Agr., Office of Expt. Stations, Bull. No. 33, p. 77. 

















VEGETABLE FIBERS —COTTON 


57 


lar cell filled with a liquid. With increase in length, the 
cell walls become thinner, and finally collapse. After the 
boll bursts, the liquid 
contents solidify by 
exposure to sun and 
air, and the dissolved 
matters are deposited 
somewhat irregularly 
on different parts of 
the cell walls, causing 
the fiber to twist. 

Dead Cotton. — Ev¬ 
ery lot of cotton con¬ 
tains ripe, unripe, and 
half-ripe cotton, due 
to different stages of 
maturity of the fila¬ 
ments on different 
parts of the same seed. In unripe cotton (Fig. i, A ), the 
fibers show no indication of tubular structure, but present 
•the appearance of broad, solid, ribbon-like fibers which are 
almost transparent, and show irregular folds. Such fibers, 
which are technically known as “ dead cotton,” are diffi¬ 
cult to dye, and may sometimes be met with as white 
specks in dyed cotton goods. 

Other Defects. — Solid places are sometimes found in the 
ripe cotton fiber; and at these points the cotton has less 
affinity for dyestuffs than at others, so that the fiber is dyed 
irregularly. Only ripe, perfect cotton fibers possess all the 
requisites for perfect spinning and dyeing. From these 




'I 






C 



Fig. i. — Cotton fiber. 

A, unripe (section); B, ripe; C, mercerized cotton. 







58 


PRINCIPLES OF DYEING 


statements it is seen that the physical structure of the cot¬ 
ton fiber, no less than its chemical composition, plays an 
important part in the process of dyeing it. 

Composition. — Cotton as it comes on the market contains 
about 8 per cent water, 87 per cent cellulose, and 5 per cent 
other substances, consisting of cotton wax, cotton oil, pectic 
acid, coloring matters, and albuminous matters. The quan¬ 
tity of water in baled cotton is not subject to great variations, 
differing in this respect from wool and silk. The substances 
other than cellulose are removed, for the most part, during 
the process of bleaching , so that bleached cotton consists of 
almost pure cellulose. 

Cotton Wax. — Cotton wax is a waxy substance, insoluble 
in water, but soluble in alcohol. It does not dissolve when 
boiled with dilute solutions of caustic soda. This wax is 
found fairly uniformly distributed over the surface of the 
cotton fiber, and it is due to this fact that raw cotton is 
wetted by water only with difficulty. 

Fatty Acids. — These are organic acids, which form 
soluble salts (soap) with caustic soda. 

Coloring Matters. — Two brown coloring matters are 
found in cotton. Egyptian cotton contains relatively large 
quantities of them, which accounts for its dark color. The 
lower grades of cotton are much darker than the finer 
qualities. 

Pectic Acid. — This is a gum-like substance, soluble 
in boiling water. It is precipitated from solution by 
acids. Alkalies combine with it, forming brown sub¬ 
stances, not so readily soluble in water as pectic acid 
itself. 


VEGETABLE FIBERS — COTTON 


59 


Cellulose.—As stated, the greater part of the cotton 
fiber is composed of cellulose. Cellulose makes up a large 
part of all vegetable fibers, and is also found in the wood 
of trees, and the stems and leaves of almost all plants. 
Cotton is the purest natural cellulose, bleached cotton 
being composed of nearly pure cellulose. Paper consists 
of more or less pure cellulose. 

With the exception of cotton and linen, all textile fibers 
in their commercial form contain large quantities of other 
substances than cellulose, so that while the properties of 
cotton and linen are those of pure cellulose modified to 
some extent on account of the structure of the fiber, the 
properties of other textile fibers may be different to a large 
extent, on account of the other bodies present. 

Preparation and Properties. — Pure cellulose may be 
prepared from cotton by washing it with alcohol and ether, 
boiling it for some time with a solution of potassium 
hydroxide, washing well, and drying. It cannot be pre¬ 
pared so easily from other materials. 

Cellulose contains carbon, hydrogen, and oxygen in 
the proportion corresponding to the formula C 6 H 10 O 5 . 
(C 6 H 10 O 5 ) x represents a molecule of cellulose. The 
molecular weight of cellulose is unknown. 

Cellulose belongs to a naturally occurring class of sub¬ 
stances known as carbohydrates, of which starch, dextrin, 
and sugar may serve as examples. It may be converted 
into a sugar, C 6 H 12 0 6 , glucose, if it is dissolved in concen¬ 
trated sulphuric acid and the solution diluted and boiled. 

(C 6 H 10 O 6 ), 4- XH 2 0 = XC 6 H 12 0 6 . 

Cellulose. Glucose. 


6o 


PRINCIPLES OF DYEING 


Cellulose is colorless, tasteless, without odor, and insol¬ 
uble in water, alcohol, ether, or other ordinary solvents. 
It is characterized by its inactivity ; methods for separating 
cellulose from plant tissues rest on the use of reagents 
which dissolve the other substances, and leave the 
cellulose unchanged. Its specific gravity is 1.5. When 
it burns freely, it does not emit any strong odor, but 
smoldering cotton gives off the characteristic odor of 
acrolein. 

Solvents for Cellulose.— Solution of cellulose is invariably 
accompanied by chemical change, which usually consists 
in combination with water, or hydration. The solutions, 
as a rule, are unstable, with the result that cellulose can 
easily be precipitated from them. Cellulose is dissolved by 
concentrated solutions of zinc chloride, copper hydroxide 
in ammonia, concentrated sulphuric acid, and some other 
solvents. 

The solution in zinc chloride is used for making cellulose 
filaments, which are carbonized for use in incandescent 
lamps. The solution is allowed to flow through a narrow 
orifice into alcohol, which precipitates a thread of hydrated 
cellulose mixed with zinc hydroxide. It is washed with 
water and acids, dried and carbonized. 

Experiment 42. — Dissolve 10 g. zinc in concentrated hydro¬ 
chloric acid, and evaporate to about 20 cc. under the hood. 
While hot, add 1 g. loose cotton, stirring carefully. What hap¬ 
pens ? Pour a portion of the solution into water; into alcohol. 
What is the precipitate ? 

Ammomacal Copper Oxide. — This solvent may be pre¬ 
pared in two ways : — 


VEGETABLE FIBERS — COTTON 


6l 


(1) Copper is covered with strong ammonia, and air or 
oxygen passed through the mixture. The copper is oxi¬ 
dized, and dissolves. 

Cu + O + H 2 0 = Cu(OH) 2 . 

(2) Copper hydroxide is precipitated by mixing solutions 
of copper sulphate, containing a little ammonia or glycerol, 
with sodium hydroxide. The precipitate is washed, and 
dissolved in strong ammonia. 

CuS 0 4 + 2 NaOH = Cu(OH) 2 + Na 2 S 0 4 . 

Ammoniacal copper oxide is a blue liquid, with a strong 
odor of ammonia. It dissolves cellulose, forming a viscous 
solution. Cellulose hydrate is precipitated when the solu¬ 
tion is poured into dilute hydrochloric acid, water, or 
alcohol, or when sodium chloride, potassium chloride, 
sugar, or some other substances are added to the 
solution. 

The Willesdcn process of water-proofing consists in pass¬ 
ing rope, canvas, or paper through an ammoniacal solution 
of copper hydroxide, and drying. The substance becomes 
coated with a film of gelatinized cellulose, mixed with cop- 

I 

per hydroxide, of a bright green color; the pores are filled, 
so that water cannot penetrate it, and the copper is a pro¬ 
tection against the attack of insects, or molds. 

Experiment 43. — Dissolve 20 g. copper sulphate and 10 cc. 
glycerol in 1000 cc. water, and add a dilute solution of sodium 
hydroxide until the liquid is faintly alkaline. (Reaction?) Allow 
the precipitate to settle, which may take several hours, pour off 
the clear liquid, and filter out the precipitate on a large filter. 
Allow it to drain well, and add the precipitate to 30 cc. of 
ammonia 0.90 sp. gr. until no more dissolves. Immerse a piece 


62 


PRINCIPLES OF DYEING 


of cotton cloth in the liquid, remove, and dry without washing. 
Describe its properties. Add some cotton wool to the solution, 
and stir well. Does it dissolve ? Pour a portion of the solution 
into water. 

Concentrated Sulphuric Acid. — Concentrated sulphuric 
acid first causes cellulose to swell, forming a gelatinous 
mass, and if this is rapidly diluted with water, a substance 
termed amyloid is precipitated. 

Vegetable parchment is prepared by precipitating amy¬ 
loid upon ordinary unsized paper, which consists mostly 
of cellulose. The paper is placed a few seconds in acid of 
the proper strength, then washed thoroughly. The prod¬ 
uct is a tough, translucent paper. Other solvents for 
cellulose, as zinc chloride, or phosphoric acid, act in the 
same way. 

Cellulose dissolves completely in strong sulphuric acid 
in a short time, cellulose sulphates being formed. If the 
solution is diluted with water and boiled for some time, the 
cellulose is converted into glucose. 

Cellulose treated with caustic soda, and then with carbon 
bisulphide, dissolves, but in time the solution decomposes 
and forms a jelly which may absorb large quantities of 
water without becoming liquid. The compound is called 
cellulose thiocarbonate, and has been proposed for use in 
the production of artificial silk. The solution (called 
viscose') is used for sizing paper, and has other uses. 

Cellulose Nitrates.—When cellulose is brought in con¬ 
tact with nitric acid at a low temperature, cellulose nitrates 
are formed. The extent of the nitration depends on the 
concentration of the acid, etc. 


VEGETABLE FIBERS — COTTON 


63 


Cellulose tetra-nitrate, C 12 H 16 0 6 (0N0 2 ) 4 , and the penta- 
nitrate, C 12 H 15 0 5 (0N0 2 ) 5 , are formed when cellulose is 
treated for a short time with a mixture of nitric and sul¬ 
phuric acids. 

(C 6 H I0 O 5 ) 2 + 4 HN0 3 = C 12 H 16 0 6 (0N0 2 ) 4 + 4 H 2 0. 

They are soluble in a mixture of alcohol and ether, and 
the solution, known as collodion, used in photography. 
When poured upon any surface, such as glass, the ether 
and alcohol evaporate rapidly, leaving a thin coating of 
nitrates, which is sensitized by the photographer. The 
solution is also used in the preparation of artificial silk 
(Chapter XX). 

Cellulose hexa-nitrate, C 12 H 14 0 4 (0N0 2 ) 6 , is made by 
treating cellulose with a mixture of nitric and sulphuric 
acids for twenty-four hours at io° C. Prepared from cotton, 
it is known as guncotton , and is used as an explosive and 
in the preparation of smokeless powders. 

Celluloid is a mixture of guncotton and camphor, pre¬ 
pared by compressing the two with the addition of alcohol. 
It is hard and brittle when cold, but at a slightly elevated 
temperature it can be molded into any shape desired. It 
is very inflammable. 

Oxycellulose. — Cellulose offers a comparatively great 
resistance to oxidizing agents, most of the reagents for 
purifying (bleaching) or isolating cellulose being oxidizing 
agents which readily attack the other substances with 
which it is mixed in the raw condition. On the other 
hand, cellulose is oxidized by nitric acid, potassium per¬ 
manganate, chromic acid, bleaching powder, and even the 
air under suitable conditions, oxycelluloses being formed. 


64 


PRINCIPLES OF DYEING 


The appearance of the cellulose depends on the extent of 
the oxidation; a moderate oxidation does not cause the 
fiber to lose its shape, or affect its strength to any great 
extent, but vigorous oxidation causes it to crumble. Some 
of the oxycelluloses are partly soluble in alkalies. 

Under certain conditions, the production of oxycellulose 
is the cause of defects in bleaching. Oxycellulose may be 
detected by the aid of certain dyes; some, as methylene 
blue or methyl violet, have a greater affinity for oxycellulose 
than for cellulose; with others, the reverse is the case. 

Experiment 44.— (1) Mix 2 g. bleaching powder, in a mortar, 
to a paste with 10 cc. water, and place a spot about the size of a 
five-cent piece on a piece of cotton cloth about 4 in. square. After 
standing half an hour, wash with water, then with water acidulated 
with hydrochloric acid, and with water made slightly alkaline with 
ammonia, and proceed to dye as in (3). 

(2) Mix 2 g. potassium bichromate and about 1 cc. sulphuric 
acid with 10 cc. water, and proceed with it as directed for the 
paste above. 

(3) Dye both pieces of cloth by boiling with per cent (of 
10-gram) methylene blue in 200 cc. water. Wash well, dry, and 
enter material in scrap-book. 

What can you say of the behavior of methylene blue toward 
cellulose and oxycellulose ? Methylene blue is a basic dye. 

Action of Acids. — Dilute mineral acids, as sulphuric, or 
hydrochloric, have little action upon cellulose, unless 
allowed to dry upon it; as the fiber dries, and the acid 
becomes more and more concentrated, the cellulose is 
affected. Fibers composed of cellulose, like cotton or 
linen, become weaker under such conditions, or fall to a 
powder, according to the conditions. The degree to which 
this change occurs depends on the temperature at which 


VEGETABLE FIBERS — COTTON 


65 


the drying takes place, and on the strength of the acid. 
Quick drying at a high temperature has a much more 
vigorous action than slow drying. If the acid is 
taken strong enough, the cellulose is completely dis¬ 
integrated, and falls to a powder which has the compo¬ 
sition C 12 H 20 O 10 . H 2 0 and is called hydro-cellulose. 

The same effect is produced by magnesium chloride, 
aluminium chloride, or ferric chloride, which decompose 
on drying, with the production of hydrochloric acid: — 
AICI 3 + 3 H 2 0 = Al(OH ) 3 + 3 HC1. 

Carbonization. — The destruction of vegetable fibers by 
the action of mineral acids at an elevated temperature is 
called carbonization, for the reason that the hydro-cellulose 
is usually black, or nearly so, and it was thought to be 
carbon. Wool is not destroyed under the conditions of 
carbonization. The applications of carbonization are : — 

( 1 ) To remove burs from wool, and cotton or linen from 
woolen rags. The rags are immersed in a mineral acid, 
and dried at a suitable temperature, or they are heated, 
and hydrochloric acid gas passed over them. Afterward, 
the hydro-cellulose dust is beaten out, and the wool re¬ 
manufactured. 

( 2 ) To produce gauze patterns in mixed cotton-wool 
goods. A design is printed upon them with a thickened 
solution of aluminium chloride, and they are dried at the 
proper temperature, when the cotton is destroyed, leaving 
the wool. 

Experiment 45. — Dilute 4 cc. cone, sulphuric acid to 100 cc., 
soak in it a piece of cotton goods, a piece of wool, and a piece of 
mixed cotton and wool. Dry at a temperature above 8o°, and 
explain results. 


66 


PRINCIPLES OF DYEING 


Action of Alkalies. — Cellulose has weak acid and basic 
properties, and will absorb acids or alkalies from very 
dilute solutions. Beyond this, dilute solutions of caustic 
alkalies have no action on cotton, whether hot or cold, and 
the same may be said of sodium or potassium carbonate, 
soap, borax, and phosphate of soda. 

Mercerization. — When cotton is treated with strong 
solutions of caustic soda and washed, it undergoes a 
peculiar change. It contracts 20 to 25 per cent in length, 
and becomes heavier, denser, and stronger. This change 
was first observed in 1850 by John Mercer, an English 
cotton printer, from whence it has the name, mercerization. 

Nature of the Change. — The cellulose first combines with 
caustic soda, forming a compound of the composition : — 

Ci 2 H 20 Oio. 2 NaOH. 

Washed with water, this decomposes with the production 
of cellulose hydrate, C 12 H 20 O 10 . H 2 0 , which is the formula 
of mercerized cotton; the gain in weight of the cotton is 
4.5 to 5.5 per cent. 

The structure of the fiber also changes. A microscopic 
examination (Fig. I, C) shows that the cell walls have 
become thicker, the central opening has decreased in size, 
and the general shape of the fiber has changed from the 
form of a collapsed tube to that of a round, rod-like 
shape. It has also received a peculiar spiral twist, which 
explains its shrinkage, by a process of drawing-in. 

Properties. — Mercerized cotton differs from ordinary 
cotton in several respects. It has a much greater affinity 
for dyes, especially for direct cotton colors like Congo red, 


VEGETABLE FIBERS — COTTON 67 

taking up more from solution, and leaving less in the dye- 
bath. 

Mercerized cotton has also a greater affinity for mordants 
than ordinary cotton. It takes up 40 per cent of tannic 
acid when the latter takes up only 20 per cent under the 
same conditions. 

Experiment 46. — Dissolve 80 g. caustic soda in 400 cc. water, 
and allow the solution to cool. Don’t get it on your hands. 

Cut a piece of unbleached cotton cloth about six inches long 
and two inches wide, measure it carefully, wet it and squeeze, then 
immerse it 5 minutes in the above solution, remove, wash, and 
dry. Remeasure. How much has it shrunk ? What per cent ? 

Immerse 4 boiled-off skeins of cotton yarn in the solution, 
work carefully for 5 minutes, remove, wash with water, and with 
water containing a little acetic acid, and dry. Save them for 
Experiment 47. Are they in any way different from ordinary 
cotton ? 

Experiment 47. — Dye a skein of mercerized cotton with \ per 
cent diamine blue BX and 10 per cent sodium sulphate in 200 
cc. water, boiling 15 minutes. Is the bath exhausted? This dye 
is a direct cotton color. 

Dye an unmercerized skein in the same way. Which skein 
takes up the more dye ? Which is darker ? 

Test fastness to acids, alkalies, and washing. Is the color faster 
on mercerized or on unmercerized cotton? 

Experiment 48. — ( a ) Work a skein of mercerized cotton 30 
minutes in 2 per cent tannic acid in 200 cc. cold water. 

Mordant an unmercerized skein (boiled-off) in the same way. 

Dye each in a separate bath of \ per cent methyl violet in 200 
cc. of water, at 50° C., working 20 minutes. Is the bath ex¬ 
hausted? Which skein takes up the more dye? The depth of 
color depends on the amount of tannic acid taken up. Which 
takes up the more tannic acid ? 


68 


PRINCIPLES OF DYEING 


Test fastness to acids, alkalies, and washing. Is the color faster 
on mercerized or unmercerized cotton? 

(b) Dye a skein of mercerized cotton with per cent methy¬ 
lene blue in 200 cc. water, at 50° C., working 15 minutes. 

Dye an unmercerized skein in the same way. What difference 
do you see ? 

Both of these dyes are basic colors. 

Mercerized cotton' is said actually to require less dye¬ 
stuff fixed upon it to produce the same shade, than other 
cotton. The saving in dye may be 10 to 15 per cent for 
light shades, 25 to 30 per cent for dark ones. The cause 
of this may be that the color is absorbed in the outer sur¬ 
face of the mercerized fiber, without penetrating to any 
extent in the canal, since the fiber is practically solid. 

Mercerized cotton has important applications which will 
be treated in a later chapter (Chapter XX). 

Tendering of Cotton. — When a fiber is weakened by 
anything which may come in contact with it during the 
ordinary process of manufacture, as in bleaching, dyeing, 
etc., it is said to be tendered. The tendering may take 
place only to a slight extent, or it may result in an actual 
destruction of the fiber. Tendered goods are found to be 
“ rotten ” after a short time. The following agencies may 
tender cotton: — 

Mildew. — Mildew is a plant, which requires warmth, 
water, and food before it can grow. Bleached cotton is 
not likely to mildew, as it contains no food for the organism. 
Dry cotton will not mildew, but in a warm, damp atmos¬ 
phere it is liable to mildew, especially goods which have 
been starched, or stiffened with gum or other vegetable 
matters, as is usually the case with finished calicoes. The 


VEGETABLE FIBERS — COTTON 


6 9 


starch or gum is a good food for the mildew. Mildew can 
easily be removed by bleaching, though the tenacity of 
the fiber is somewhat impaired. 

Frost. — Wet cotton, exposed to a freezing temperature, 
is liable to damage. The water sucked into the canal of 
the fiber by capillary attraction, expands with great force, 
and bursts the fiber asunder. 

Crystals of Salts. — If crystals are allowed to form in 
the canal of the cotton fiber, it may be weakened. The 
cell walls are penetrated and cut by the sharp edges of the 
crystals when they are closed in upon them by any strain. 
Crystals may be formed in the fiber when cotton is treated 
with solutions containing large quantities of salts of any 
kind, and allowed to dry without washing. 

Acids. — Whenever mineral acids come in contact with 
cotton, it afterwards must be washed thoroughly, since 
they will tender the fiber if allowed to dry upon it. 

Acetic acid has no action on cotton, nor has oxalic, 
tartaric or citric acids under ordinary conditions, but 
the last three may tender cotton at a high tempera¬ 
ture, as when steamed with it under pressure. Cotton 
is steamed under pressure sometimes when it is printed, 
and as these acids are used in printing, there is danger of 
damage. 

Salts, as aluminium chloride, ferric chloride, and magne¬ 
sium chloride, which decompose with the formation of free 
acids, will tender cotton if dried upon it. 

Oxidation. — The cotton fiber is liable to be tendered by 
oxidation during processes of bleaching and dyeing. 
Damages by oxidation during bleaching are discussed in 
Chapter XI. 


;o 


PRINCIPLES OF DYEING 


Cotton Manufacture. — Loose cotton passes first to the 
opener , where it is subjected to the action of a beater, and 
a blast of air, which partially cleans it, and separates its 
matted flakes. It then goes to the tapper , which cleans it 
further, from which it comes out as flat sheets, which are 
rolled up into laps. 

The cotton passes from the lapper to other machines 
which clean it further, then to machinery which cards it 
with wire teeth, so that the fibers are laid parallel. It is 
then formed into a loose, continuous strand called a sliver , 
which is drawn, and finally twisted into yarn, passing 
through a number of machines. 

Yarn is wound, as spun, on wooden bobbins, or on a 
hollow pasteboard tube, in which form it is called the cop. 
In the cop, the threads are wound tightly one on the other, 
forming a solid, compact spindle, with a hollow core. 

In forming skeins, a single cop or bobbin is wound 
off in a circular form, from 54 to 72 in. in circumference. 
A skein is composed of a single, continuous thread. In 
forming warps, from 50 to 1000 or more cops are wound 
off together, producing a bundle of parallel strands, some¬ 
times several thousand yards long. 

The warps and skeins are dyed or sized if desired. 

Sizing consists in passing the yarn through starch paste 
or other sizing materials, the primary object of the sizing 
being an increase in strength, so that the threads will not 
break under the tension to which they are subjected in the 
loom. The size also lays the loose fibers {matte) on the 
yarn. The size sometimes has substances added to it to 
increase the weight of the yarn. 

Yarn in skeins is used for weft, when it is called filling , 


VEGETABLE FIBERS —COTTON 


71 


and it is wound off for the shuttle. The warp is beamed; 
that is, wound on iron spools or beams a little longer than 
the cloth is to be wide, with the threads untangled, arranged 
parallel, and colored threads in the places they are to have 
in the cloth. It is then ready for the loom. 

Unsized yarn for warps, dyed or undyed, is sometimes 
wound off into section warps, an operation similar to beam¬ 
ing, except that part of the total number of threads is 
wound off on several beams. It is then sized, passing on 
to the beam. 

After weaving, the final series of operations is finishing; 
the number of operations involved vary according to the 
kind and grade of material produced. In some cases, the 
loose fibers are burned off; in others, the material is 
napped , that is, a nap or felt is formed, as in flannelettes 
or cottonades. It may be sized with starch or other sub¬ 
stances, stretched to its full width on the tentering ma¬ 
chine, and ironed by passing between two hot rollers, 
calenders , which press upon each other with considerable 
force. 

Count , ply , and twist refer to the yarn. 

The twist varies with different kinds of yarn; the more 
it is twisted, that is, the harder the twist, the less easily is 
the yarn penetrated by the solutions used by the dyer. 
Warps always have a harder twist than filling (yarn for 
the weft), or hosiery yarn. 

The count of a yarn indicates its fineness ; the larger the 
count, the finer the yarn. With cotton yarn the count 
indicates the number of hanks of 840 yd. to a pound. 
Thus 6o’s cotton is a yarn that requires 60 hanks of 840 
yd. to weigh a pound, or 60 x 840 yd. weigh a pound. 


72 


PRINCIPLES OF DYEING 


io x 840 yd. of 10’s cotton weigh a pound. The count of 
wool and linen is different from that of cotton. 

The count of a cotton yarn may be found as follows: 
If y is the count, y x 840 yd. weigh a pound, or 7000 gr., 
or y x 120 yd. weigh 1000 gr. If we measure off 120 yd. 
and find its weight to be (a) grains, then the count of the 
1000 

yarn y = -- 

a 

Or measure off 184 yd. and divide 100 by the weight in 
grams. 

Ply indicates the number of strands composing a yarn. 
Two-ply yarn is composed of two strands twisted together, 
and §0 on. 3/30’s cotton means that three strands of 30 
count are twisted together, forming a compound yarn of 
10 count. 

The dyer may receive the material at any stage of its 
manufacture; as loose cotton, sliver or slubbing, yarn in 
the form of cops, skeins or warps, and as cloth. 



CHAPTER VIII 


LINEN-OTHER VEGETABLE FIBERS 

Linen is the vegetable fiber next in importance to cotton. 
It is prepared from the stem of the flax plant, Liniurn nsi- 
tatissimum. Very little linen fiber is produced in the United 
States. It is grown extensively in Northern Europe and 
Ireland. 

The flax plant, besides the fiber, contains from 70 to 80 
per cent of wood, pith, and other substances. The sepa¬ 
ration of the fiber requires a number of operations. The 
plant is pulled up by the roots, and drawn through coarse 
combs to remove seeds. It is next retted , a kind of fermen¬ 
tation which softens or destroys the substances which 
cement the fibers together and to the woody portion of the 
plant. After retting, various mechanical processes are 
employed to detach the ligneous matter from the fiber. 
Breaking consists in crushing the flax between grooved 
rolls, to break the woody particles; after which it is 
scutched , that is, the woody particles are beaten out by 
hand or by machines. 

The last operation, heckling , consists in drawing the flax 
through coarse combs, then through finer and finer ones, 
until a degree of fineness suitable for spinning is attained. 

Microscopic Appearance.—The linen fiber as spun con¬ 
sists of numbers of short cells, gummed together to form 

73 


74 


PRINCIPLES OF DYEING 


one long fiber. This is shown by a cross-section of the 
fiber (Fig. 2). 

The individual fibers can be separated by treatment with 
dilute chromic acid. They appear as straight fibers, with 
a minute central canal. Their length is .8 to 
1.5 in., diameter .0006 to .00148 in. 



Composition. — Linen, unbleached, contains 6 to 
8 per cent water, 62 to 77 per cent cellulose, and 
15 to 30 per cent of other substances, mostly pec- 
tic in nature, which are more difficult to remove 
than in the case of cotton. The cellulose and pec- 


'1 , i t| tic substances appear to be in chemical combination. 


Properties. — Linen is stronger 
and more durable than cotton, 



less pliant and elastic, and pos¬ 
sesses a peculiar luster. It is 
a better conductor of heat than 
cotton, which explains why linen 
articles are colder to the touch 
than cotton. 


Fig. 2. — Linen fiber. 


The cellulose of linen has the same composition and 
general properties as cotton cellulose. It is soluble in 
solutions of zinc chloride, ammoniacal copper oxide, and 
in concentrated sulphuric acid; forms nitrates and oxy- 
cellulose; is carbonized by acids; is oxidized by bleach- 
ing-powder, etc. 

Linen is more easily tendered than cotton; the reagents 
act upon the substance which cements the individual cells 
together, separating them, and thus weakening the com¬ 
pound fiber. 











LINEN —OTHER VEGETABLE FIBERS 


75 


Toward dyes and mordants, linen behaves like cotton, 
but it is more difficult to dye. The difference is probably 
due to the difference in the physical structure of the two 
fibers. We have seen that the structure of cotton influences 
its dyeing properties, in that unripe fibers, and solid places 
in the fiber, are dyed with difficulty. The presence of 
pectic substances on the fiber may also aid to render linen 
harder to dye than cotton. Dyeings on linen are usually 
required to have a high degree of fastness. 

Detection of Cotton in Linen. — The presence of cotton 
in linen may be detected by microscopic examination. A 
number of other tests are also available, as for example: — 

(a) The sample is placed in olive oil, removed and 
pressed between blotting paper. The linen becomes semi¬ 
transparent, while the cotton remains opaque. 

($) The sample is dipped in a i per cent alcoholic solu¬ 
tion of fuchsine, washed, and laid in ammonia. Cotton 
remains uncolored, linen becomes rose-red. 

j u te. —Jute is the fiber from the stem of several species 
of Corchorus, and comes most largely from India. It has 
been grown experimentally in the United States. Like 
flax, the plants contain much other material besides the 
fiber. The plants are steeped a week or more in stagnant 
water (retted); the bark is stripped, and the fiber rinsed, 
heckled, and dried. It is light yellow and has a high 
luster. Like linen, the filaments used (3 to 6 ft. long) 
are composed of bundles of small cells about an inch long. 

Composition and Properties. —The jute fiber is fine and 
silky, but it cannot withstand dampness, and deteriorates 


76 


PRINCIPLES OF DYEING 


rapidly under the best conditions. The bleached fiber also 
loses its whiteness, and in time oxidizes until it presents 
a yellowish brown color. Jute is used to a great extent for 
the manufacture of cotton bagging, matting, coarse cloth, 
and to some extent for curtains, carpets, and upholstery. 

Jute differs from cotton and linen in that it contains no 
cellulose as such. It contains 9 to 12 per cent water, 86 
to 89 per cent of a ligno-cellulose, and 2 per cent of ash, 
fat, and substances soluble in water. 

The ligno-cellulose of jute is a compound of cellulose 
with lignified tissue, called bastose. Bastose is very sus¬ 
ceptible to the action of acids and alkalies, and is easily 
destroyed by mineral acids. It absorbs chlorine with great 
avidity, and for this reason requires precautions when 
bleached with bleaching-powder. 

Jute resembles cotton which has been mordanted with 
tannic acid, and it can be dyed directly with basic colors. 
It has also some affinity for certain acid colors. 

Hemp.— Hemp is the fiber from the hemp plant, Can¬ 
nabis sativa , largely cultivated in Russia and India, and to 
a considerable extent in the United States. The methods 
for obtaining the fiber from the plant are similar to those 
used for flax. 

Hemp is principally used for the manufacture of ropes, 
canvas, and bagging. It is seldom bleached or dyed, as 
the fiber is too coarse. The fiber contains cellulose. 

China Grass. — China grass or ramie is the fiber from the 
stem of a nettle, Boehrneria nivea, which is grown mainly 
in China, though it will grow well in this country. The 
fiber is difficult to detach from the woody matter; retting 


LINEN —OTHER VEGETABLE FIBERS 


77 


separates the fiber into its component cells, which cannot 
be separated from the stem and bark. The usual method 
of separation is to crush or beat the stalk while green, and 
wash out the broken wood, etc., by a powerful jet of water. 

The fiber of China grass has a high luster and silky 
appearance, is little affected by moisture, easy to bleach, 
but difficult to dye without injuring its luster. It has a 
great variety of uses ; curtains, laces, napkins, carpets, cord¬ 
age, etc. The fiber is nearly pure cellulose. 

Other Fibers. — Many other fibers have some commercial 
value, but most of them are seldom dyed or bleached. 

Sun hemp is a bast fiber, used in India for cordage and 
sackcloth. Manila hemp is used for ropes and twine in 
this country, though it is said to be made into fine muslins 
in Manila. Sisal hemp , New Zealand flax , and the fibers 
obtained from the leaves of the aloe, agave, banana, palm, 
and the fibrous material which surrounds the cocoanut, 
have their uses. 

Other Vegetable Materials. — Straiv (for hats) is com¬ 
posed largely of cellulose, and is dyed and bleached. 
Paper is also more or less pure cellulose, and is often 
colored. 


CHAPTER IX 


ANIMAL FIBERS-WOOL 

The animal fibers are totally different from the vegetable 
fibers in their composition and properties. Unlike vege¬ 
table fibers, they contain a large percentage of nitrogen ; 
dissolve in warm solutions of alkalies; are not “ carbon¬ 
ized ” by acids; have a great affinity for dyes and mor¬ 
dants. The methods of preparing, bleaching, mordanting, 
and dyeing animal fibers are, as a rule, quite different 
from those used for vegetable fibers. 

Wool. — Strictly speaking, wool is the hair of the sheep, 
but the hair of certain goats (cashmere, mohair, and 
alpaca) and of the camel are generally classed under the 
same category. Fur consists principally of the hair of the 
rabbit or hare and is extensively employed in the manufac¬ 
ture of the better class of felt hats. 

Grades. —The grade of wool depends upon the length of 
the staple, its fineness, luster, strength, elasticity, color, 
curl, etc. It varies in different parts of the same fleece. 
Wool from diseased sheep is of inferior quality, being 
duller and having less affinity for dyestuffs than ordinary 
wool. Sheep pelts are often soaked in lime-water or 
sodium sulphide to loosen the wool, and the wool is pulled 
out before making leather of the skin. Such wool is 
known as pulled wool, and is of inferior quality. 

Wool is divided into long-stapled and short-stapled 

78 


ANIMAL FIBERS —WOOL 


79 


varieties. These two varieties are usually separated before 
being spun. The long-stapled fibers are longer than ij 
in., are made up into tops and spun into worsted yarn; 
the shorter fibers (noils) are carded and spun into woolen 
yarn. In worsted yarn the fibers are more or less par¬ 
allel ; in woolen yarn they lie in all directions. 

Microscopic Appearance. — When seen under the micro¬ 
scope (Fig. 3), the wool fiber appears in the form of a 
solid rod-shaped substance, the surface of which is covered 
with broad scales, all projecting 
in the same direction, like the 
scales of a fish. A more careful 
examination shows that a single 
fiber consists of a vast number of 
narrow individual cells, tapering 
toward each end. The interior 
cells appear to have a greater 
attraction for dyes than do the 
outer horny scales, and acids and 
some other additions to the dye- 
bath are supposed to aid in dyeing, 
in part by raising the scales, thus 
exposing the interior cells to the 
action of the dye. 

If a single wool fiber is taken between the thumb and 
finger of each hand and drawn gently, the end nearest the 
root remains stationary, while the other end slips. This is 
caused by the roughness or scales on the fiber. If, when 
wet, wool fabrics are subjected to friction, especially in pres¬ 
ence of soap or of soap and soda, the friction of the fibers is 







8o 


PRINCIPLES OF DYEING 


greater in one direction than in the other, the scales inter¬ 
lock, and the material felts , becoming thicker, and assum¬ 
ing a denser appearance. Milling is used to produce this 
effect in the manufacture of broadcloths, flannels, and some 
other classes of goods. In some other classes of goods 
felting is a disadvantage, and must be prevented as far as 
possible. 

The average length of the various classes of wool varies 
between i-J and 7 inches, and the diameter from .004 to 
.0018 inch. 

Kemps. — Kemps are smooth, white fibers, void of inter¬ 
nal structure, and practically without “scales,” since the 
scales are completely attached to the body of the fiber. 
They are frequently met with in the coarser varieties of 
wool, especially in mohair. A fiber may be normal up to 
a certain point, and thence kempy to the end, or even nor¬ 
mal at both ends and kempy in the middle. 

Having no scales, kemps have no felting power, and in 
dyeing they also come out uncolored or considerably lighter 
than the other fibers. Kemps are usually eliminated in the 
process of combing. Kemps have the same composition 
as ordinary wool. Their different behavior in dyeing is 
due to their impenetrable structure. They are analogous 
to the solid places found in cotton. 

Dead fibers , so called, sometimes occur in wool. They 
are fibers which have been pulled out, or have died, before 
the wool was cut; they are harsh and weak, and are said 
not to dye readily. 

Physical Properties. — Wool is hygroscopic, and takes 
up water from the air. At ioo° C., wool becomes plastic 


ANIMAL FIBERS —WOOL 


8 I 


and can be made to assume any shape desired, which it 
will retain if allowed to cool in this condition. Advantage 
is taken of this property, ( a ) in increasing the length of 
yarns ; ( b ) in preventing the shrinkage of mixed goods con¬ 
taining wool when they are washed; and ( c ) in all the pro¬ 
cesses of wet finishing of woolen goods. 

Experiment 49. — Place a horn spoon or spatula in a beaker 
of boiling water, remove it in 15 minutes, and bend it. When 
cool, its former shape cannot be restored unless it is heated again. 
Horn is similar in composition to wool, and the experiment illus¬ 
trates the plasticity of wool. 

Composition of Raw Wool.—Wool comes on the market 
in two conditions; ivashed , in which it was washed on the 
sheep before clipping, and unzvashed. 

Unwashed wool, or wool “in the grease," as it is called, 
contains water, fiber, and from 30 to 80 per cent of dirt 
and other substances which can be removed by washing, 
so-called yolk and suint. 

As stated, the water content of wool varies according to 
the humidity of the atmosphere. In warm, dry weather it 
may contain 8 to 12 per cent, but in damp weather it may 
contain 30 per cent. Wool is sold on a basis of 18.25 P er 
cent moisture. The quantity of moisture is determined at 
the time of the sale, an operation called “conditioning," 
which simply consists in determining the loss in weight of 
a sample dried at 105-110°. 

Yolk consists of higher solid alcohols, especially choles¬ 
terol, free and in combination with fatty acids. It is 
insoluble in water, but forms an emulsion with soap solu¬ 
tions, and so can easily be removed by soap. Benzene 
and carbon bisulphide dissolve yolk. 


G 


82 


PRINCIPLES OF DYEING 


Suint consists of the potassium salts of oleic, stearic, 
valeric, and acetic acids. It is soluble in water, and being 
a kind of natural soap, it removes the yolk, or a portion of 
it, when wool is washed with water. 

The dirt is picked up by the wool and adheres to it 
mechanically. 

The composition of raw wool varies considerably. It 
may contain : — 

Yolk and suint . . . . 12 to 47 per cent. 

Wool fiber.15 to 72 per cent. 

Dirt.3 to 24 per cent. 

Composition of the Fiber. — Chemically, the wool fiber 
differs from all others in its composition and properties. 
It consists of keratine, which is found also in all horny 
tissues, such as whalebone, horn, feathers, etc. The wool 
fiber varies in composition; thoroughly cleansed, it con¬ 
tains, on the average:— 


Carbon.50 per cent. 

Nitrogen.15 to 17 per cent. 

Hydrogen.7 per cent. 

♦ 

Sulphur.2 to 4 per cent. 


The presence of sulphur in wool distinguishes it from 
silk. Sulphur is detected in wool by boiling it with a 
solution of sodium plumbite, when lead sulphide is pre¬ 
cipitated, causing the solution to turn black. 

Sodium plumbite is prepared by treating lead acetate, or 
some other soluble lead salt, with sodium hydroxide: — 

Pb(C 2 H 3 0 2 ) 2 + 4 NaOH = 2 NaC 2 H 3 0 2 + Na 2 Pb 0 2 -f 2 H 2 0 . 







ANIMAL FIBERS —WOOL 


83 


Experiment 50. — Place about a gram of lead acetate in a test- 
tube with 5 or 6 cc. water. Add a dilute solution of sodium 
hydroxide until the precipitate, which first forms, redissolves. 
(Reaction.) Then add a piece of wool, and heat to boiling. 
What happens ? The black precipitate is lead sulphide. 

The presence of sulphur in wool sometimes gives rise to 
trouble in dyeing. If the water used contains lead (from 
pipes, etc.), the color of the wool is dulled by the forma¬ 
tion of lead sulphide. The trouble can be avoided by the 
addition of sulphuric acid to the dye-bath, when lead sul¬ 
phate is formed. 

Solution of Wool. — Like cotton, wool cannot be dissolved 
without chemical change. Concentrated mineral acids dis¬ 
solve wool completely. The action takes place slowly at 
the ordinary temperature, more rapidly on heating. When 
the solution is diluted and mixed with acid colors, insoluble 
compounds (lakes) are precipitated. 

Nitric acid dissolves wool with copious evolution of 
fumes. The solution has a yellow color. 

Solutions of alkalies , as caustic soda, or caustic potash, 
dissolve wool readily when the solution is heated. At the 
boiling temperature, one part of caustic soda will dissolve 
100 parts of wool. The action decreases as the tempera¬ 
ture sinks. At o° C. wool is only slightly affected even 
by concentrated alkalies. 

Experiment 51. — Dissolve 2 g. caustic soda in 100 cc. 
water, and add a piece of wool. Heat to a boil, and boil some 
minutes. What happens? Repeat, using cotton. How can 
you separate cotton and wool? Try the action of nitric acid on 
wool. 


8 4 


PRINCIPLES OF DYEING 


The solution of wool in alkalies contains a number of 
organic acids, the most important of these being lanuginic 
acid. 

Lanuginic acid is a yellowish brown powder, soluble in 
water, and precipitated by many dyes, in the form of 
intensely colored lakes. It is precipitated by tannic acid, 
bichromate of potash, and the acetates of aluminium, iron, 
chromium, and copper, all of which are absorbed by the 
wool fiber. The existence of this substance with such 
properties is evidence in favor of the chemical theory of 
dyeing as applied to wool dyeing. 

Chlorinated Wool.—Wool absorbs chlorine readily, and 
is destroyed by an excess of it. By careful treatment with 
bleaching-powder it may be made to absorb as much as 33 
per cent of its weight of chlorine. Chlored wool resembles 
silk in some of its properties ; it has an increased luster, 
but has become harsh and yellow, and lost its power of felt¬ 
ing. It dissolves readily in ammonia with the evolution of 
nitrogen gas. It has also an increased affinity for certain 
coloring matters, and practical use is made of this property 
in preparing delaines for printing and for producing two- 
colored effects on woolen piece goods. In the latter case 
the wool is chlored before weaving, and dyed after weav¬ 
ing. The chlored wool takes up a greater quantity of the 
dye than the untreated wool. 

Experiment 52. — Work two wool skeins 15 minutes in a 
1 per cent solution of hydrochloric acid. Squeeze. Save the 
solution. 

Grind 10 g. bleaching-powder to a paste with 20 cc. water, 
mix with 500 cc. water, and allow to settle. Take 100 cc., dilute to 
300 cc., and work the two skeins in it 20 minutes. Work again in 


ANIMAL FIBERS —WOOL 85 

the first bath 10 minutes, squeeze, and wash 3 or 4 times. The 
product is chlored wool. 

Dye a chlored and an unchlored skein together in a bath of 
1 per cent diamine scarlet, 10 per cent Glauber’s salt, and 1 per 
cent acetic acid in 500 cc. water, working carefully and boiling 
half an hour. 

Dye a second chlored and unchlored skein in a bath of 2 per 
cent naphthol green B, 10 per cent Glauber’s salt, and 2 per cent, 
sulphuric acid in 500 cc. water. Test fastness to washing. 

Diamine scarlet is a direct cotton color; naphthol green, an 
acid color. What effect has chloring on the affinity of wool for 
dyes? 

Oxidation of Wool. — Wool is not readily oxidized; it may 
be boiled with bichromate of potash and sulphuric acid, in 
not too great quantities, without oxidation. If an exces¬ 
sive quantity is used, the wool is “overchromed”; when 
it has undergone this change, it can no longer be dyed 
black with logwood. 

Boiled with permanganate of potash, the wool turns 
brown, and is tendered through oxidation. 

Tendering of Wool. — Wool is tendered by a number of 
reagents. Caustic alkalies in warm or hot solution readily 
tender wool. Sodium carbonate does not tender wool at a 
moderate temperature, if the action is not too prolonged, 
but in boiling solution tenders wool readily. 

Soap, phosphate of soda, borax, ammonia, and ammonium 
carbonate have little action upon wool, even in boiling 
solution, unless the soap is impure and contains sodium 
carbonate or caustic soda. Soap, phosphate of soda, and 
borax are often used when it is necessary to dye wool in 
an alkaline solution. 


86 


PRINCIPLES OF DYEING 


Absorptive Power. — Wool has an affinity for acids and 
absorbs them from dilute solutions. The acid absorbed 
cannot be readily extracted even by boiling water, and the 
wool can be dyed with acid dyes in neutral solution. (See 
Exp. 21.) Sulphuric acid, tartaric acid, and hydrochloric 
acid are taken up in this way. 

Sulphurous acid is also absorbed and retained tenaciously 
by wool. Wool bleached with sulphurous acid, if it is to 
be printed, or woven with colored materials, must be treated 
with chloride of lime or hydrogen peroxide to destroy the 
excess of sulphurous acid. Otherwise the sulphurous acid 
may prevent the fixation of certain coloring matters, or- 
cause them to fade, owing to its reducing action. 

Tannic acid in cold solution has little effect on wool, but 
when boiled with it, the wool absorbs tannic acid, and its 
properties are altered. 

Metallic salts , especially those of trivalent elements, such 
as aluminium, chromium, and iron, are decomposed by the 
wool fiber, and combine with it. 

Behavior to Dyes. — We have seen that wool has a direct 
affinity for most dyestuffs, taking them up with such 
avidity, indeed, that in most cases its action must be tem¬ 
pered or moderated, so that the wool which first comes in 
contact with the dye will not get more than its share, and 
the goods be unevenly dyed. 

We have seen that the direct cotton colors, the acid dyes, 
and the basic dyes can be fixed upon wool without the 
mediation of any mordant. The mordant colors, indeed, 
require a mordant, but it must be remembered that it is the 
compound of the mordant with the dye which produces 


ANIMAL FIBERS —WOOL 87 

the characteristic color, and that the dyestuff itself is, as a 
rule, valueless as a color. 

Detection of Wool. — The simplest test for distinguishing 
between animal and vegetable fibers, is to pick out a few 
threads and burn them. The appearance and odor are 
characteristic. 

Cotton , or any vegetable fiber, may be detected in wool 
or silk by boiling the material with a solution of caustic 
soda, when the wool dissolves completely, while the cotton 
is unaffected (see Exp. 49). 

In silk , wool may be detected by boiling the solution 
with sodium plumbite; if wool is present, a black precipi¬ 
tate of lead sulphide is formed. 

Carbonization. —Wool is separated from cotton for the 
purpose of remanufacture by the process of carbonization , 
which has already been mentioned under the head of 
Cotton. The material is saturated with sulphuric acid of 2° 
to 8° Tw., or hydrochloric acid, and dried. Drying cham¬ 
bers and continuous machines, such as are used in drying 
raw cotton, are used. After the operation, the cotton is 
beaten out. 

Carbonized wool is less strong and lustrous than the 
fresh fiber, as the acid affects it to some extent. In dyeing 
it with acid dyes, caution is necessary. 

Shoddy and Mungo. — Woolen rags from hosiery, flan¬ 
nels, and other soft woolen fabrics, are shredded for 
the purpose of remanufacture, and the product is called 
shoddy. Mungo is made from the shreds and clippings 
of milled woolen cloths. Wool-extract is prepared from 
mixed rags, which are carbonized to remove the vegetable 


88 


PRINCIPLES OF DYEING 


fibers. These products, being made from colored rags, 
are more or less dark in color, and require precautions in 
dyeing. 

Rare Wools. — Cashmere wool is the product of a goat 
which abounds in the mountains of Thibet. Mohair is the 
wool of the angora goat, imported from Turkey and South 
Africa. It is characterized by its striking luster. Alpaca 
is the hair of a goat. Camel's hair is a coarser hair, and 
is collected when the animals shed it. Fur consists prin¬ 
cipally of the hair of the rabbit and hare, and is extensively 
used in making the better class of felt hats. 

Wool Manufacture. — Long wool fibers are combed and 
spun into worsted yarn, in which the fibers are parallel; 
the short fibers are carded, and spun into woolen yarn, in 
which the fibers are less regularly arranged. The loose 
wool passes through the intermediate stages of tops and 
slubbing before it becomes yarn. As the fibers are stiff, 
they are usually softened with oil before spinning. 

Warps of wool are sized with gum or glue, to strengthen 
the yarn. For many kinds of cloth, the woven fabric 
passes through an operation known as milling. The cloth 
is wetted with soap and water, and is subjected to friction 
between two rollers until the material has felted to a suffi¬ 
cient extent. 

Wool is dyed in the form of loose wool, tops, slubbing, 
skeins, warps, and cloth. 

The count of worsted yarn is the number of hanks of 
560 yards to the pound. The size of woolen yarns is in¬ 
dicated in Philadelphia and vicinity by the cut; the cut 
indicates the number of cuts of 300 yards to the pound. 


ANIMAL FIBERS —WOOL 


89 


Elsewhere, the run system is used, the run being 1600 
yards. The run is divided into halves, quarters, and 
eighths. Two thousand yards of i^-run yarn weighs a 
pound. A pound of 6-cut woolen yarn contains 6 x 300 
yards. 

Fastness to Milling. — Dyes applied to wool before it 
reaches the cloth stage, as a rule, must be fast to milling, 
i.e. they must not run or bleed during that operation. 
Dyed cotton mixed with the wool must stand the same test. 

The test is as follows : Plait together with yarn or mix 
with undyed material, knead for 20 minutes in a solution 
of 10 g. soap and 1 g. soda per liter of water, allow to lie 
10 minutes, rinse, and dry. 


CHAPTER X 


SILK 

Silk is the fibrous substance which the silkworm spins 
to form its cocoons. Silk resembles wool in many respects. 
The numerous kinds of silk may be divided into two classes 
— artificially reared and wild silk. The principal species of 
silkworm feeds on the leaves of the white mulberry, and is 
reared in China, Japan, India, Italy, the south of PTance, 
Greece, and to a slight extent in the United States. In Asia 
the worms are reared in the open air, but in Europe this is 
done in sheds. The eggs are placed on shelves, and the 
temperature of the room raised from i8° co 25° in twelve 
days. When the eggs hatch, the caterpillars are removed to 
another room, and fed on the leaves of the white mulberry. 
They grow rapidly, changing their skin every 4 to 6 days. 
At the end of 30 to 33 days the mature worms creep into 
birch twigs, or bundles of broom or heather, where they 
spin themselves into cocoons. The spinning lasts three 
days, generally, but in order to be more sure that all the 
worms have ceased spinning, five days are allowed to 
elapse before the cocoons are collected. Some of the 
finest having been selected for breeding, the rest are killed, 
either by exposing them in stoves to a temperature of 
60-75° for three hours, or by steaming them for ten 
minutes. 


90 


SILK 


91 


How the Worm Spins. — Before the silk is spun, it is 
found in the worm as two liquids, one a clear, colorless 
liquid, the other colorless or yellow, which are both secreted 
from two glands, one on each side of the head, communica¬ 
ting with a capillary orifice in the head. The silk liquid 
solidifies on coming in contact with the air, forming a uni¬ 
form double fiber, which in some places may be seen sep¬ 
arated into two filaments. 

Preparation of Silk. — After the cocoons have been 
sorted, the silk is 7 'eelcd off. After removing the outer 
portion of the cocoon, which consists of a loose tangle of 
threads, a number of cocoons are placed in warm water, to 
soften the gum, and the ends of the fibers from 4 to 18 
cocoons are collected and reeled off as one thread. The 
length of the fiber in a single cocoon varies from 1000 to 
4000 yards. 

Grades of Silk. — Orgazine or warp silk is composed of 
the reeled off fibers of a number of cocoons. Tram , or 
weft silk, contains a smaller number of fibers. The outer 
portions of the cocoons are used in the manufacture of 
floret silk. Cocoons pierced, or otherwise defective, and 
the innermost layers of the cocoon are used for spun silk. 
They are fermented with water, boiled with soda, washed, 
dried, combed, carded, and spun. 

The count of spun silk is the number of hanks of 840 
yards to the pound. The size of raw silk is measured by 
the weight of 1000 yards in drams avoirdupois. A pound 
of i-dram silk contains 250,000 yards. 

Physical Properties. — Like wool, silk is hygroscopic, 
and absorbs moisture from the air. It can be made to 


92 


PRINCIPLES OF DYEING 


absorb up to 30 per cent of water without feeling damp. 
The legal quantity of water in silk is 10 per cent, and it is 
sold on that basis, the moisture in each purchase being 
determined in “conditioning” establishments, as is the 
case with wool. 

Silk is a bad conductor of electricity, and easily becomes 
electrified by friction. This is a disadvantage in manufac¬ 
turing it, but it is overcome to a great extent by keeping 
the air of the room moist. 

Silk is very strong; it is elastic, and can be stretched 
one-fifth to one-seventh of its length without breaking. 

Under the microscope silk appears as a structureless, 
transparent, rod-like fiber with a smooth surface. It has 
an average diameter of .007 inches. 

Composition. — Silk contains water, silk gum, and silk 
fiber, coloring matters, fats, and ash. 

Water , as stated, varies with the dampness of the atmos¬ 
phere. 

Silk gum, or silk glue, is the outer covering of the fiber. 
It is soluble in boiling water, or a solution of soap, and 
makes up from 20 to 25 per cent of the raw silk. It con¬ 
sists mostly of sencine , C 15 H 25 N 5 O g , which is precipitated 
from solution by alcohol, tannin, and metallic salts. 

Silk fiber , when purified from silk gum by treatment 
with hot water, and washed with alcohol and ether, has 
the formula C 15 H 23 N 5 0 6 , and is termed fibroine. 

Ash. —The silk fiber contains a small quantity of inor¬ 
ganic mineral substances, from 0.7 to 1 per cent, forming 
the ash. 

Raw silk also contains small quantities of waxy, fatty, 


SILK 


93 


and resinous matters, and in case of yellow silk, a yellow 
coloring matter. 

Solution of Silk. — Silk can be dissolved in several 
reagents, at the same time undergoing a chemical change. 
Concentrated mineral acids dissolve silk readily and rapidly. 
Hydrochloric acid could be used to separate wool from silk, 
as the silk dissolves in a short time, while the wool requires 
several days. 

Solutions of alkalies do not dissolve silk, or affect it 
appreciably when cold, even when concentrated, but hot 
solutions dissolve it readily, though not so readily as they 
do wool. Sericinic acid is a product of this action. It pre¬ 
cipitates coloring matters from solution. 

Experiment 53. — Boil a piece of silk with a 10 per cent solu¬ 
tion of caustic soda. What happens ? 

Place a piece of silk and a piece of wool in concentrated hydro¬ 
chloric acid. The silk dissolves almost immediately. Pour the 
solution into water. What happens? Let the wool and acid 
remain in Contact until it dissolves. It will take several days. 

Basic zinc chloride in boiling solution dissolves silk, but 
does not affect cotton or wool. Hence it can be used to 
separate silk from these fibers. 

Experiment 54. — The basic zinc chloride is prepared by heat¬ 
ing 100 g. zinc chloride and 4 g. zinc oxide, in 100 cc. water until 
solution is effected. 

Try its effect on pieces of cotton, wool, and silk. 

Nickel hydroxide dissolved in ammonia, dissolves silk 
very rapidly, and will not dissolve cotton or wool. It is 
used for the separation of silk from wool. 


94 


PRINCIPLES OF DYEING 


Experiment 55. — Dissolve 10 g. nickel sulphate in 1000 cc. 
water, and add a solution of caustic soda until the liquid is 
slightly alkaline. Allow the precipitated nickel hydroxide to 
settle. (Write reaction.) 

Pour off the clear liquid, filter off the precipitate, and wash it 
with water. The precipitate is then put into a 100 cc. flask, 50 cc. 
ammonia (sp. gr. 0.90) added, and the volume made up to 100 cc. 
When the nickel hydroxide has dissolved, try its effect upon small 
pieces of silk, wool, and cotton. 

Zinc chloride , in concentrated solution, and copper hydrox¬ 
ide dissolved in ammonia, dissolve silk and cotton. 

Copper hydroxide in caustic soda , prepared by adding 
glycerol to a solution of copper sulphate, and then a solution 
of caustic soda until the precipitate which first formed just 
redissolves, is said to dissolve silk without affecting cotton. 

Absorptive Power. — Like wool, silk has considerable 
affinity for many compounds. 

Acids are absorbed from dilute solutions, and retained 
tenaciously. The luster of the silk is increased, and it 
acquires a peculiar feel, and emits a peculiar crackling 
sound when compressed. The scroop feel , as it is called, is 
frequently desired. Silk is usually brightened or given the 
scroop feel after dyeing, by working it in a dilute solution 
of acetic, sulphuric, or tartaric acid for a short time. Tar¬ 
taric acid gives the best results. It is dried without wash¬ 
ing. The effect of acetic acid disappears after a time, but 
that of the others is permanent. 

Tannic acid is absorbed by silk, a property made use of 
in weighting silk (Chapter XII). 

Metallic Salts. — Silk behaves like wool toward metallic 
salts used for mordants. It decomposes the salts even in 
cold solution. 


SILK 


95 


Coloring Matters. — Silk behaves like wool toward col¬ 
oring matters in general, but has less affinity for acid 
colors, and a greater affinity for basic colors. 

Tendering of Silk. — Hot solutions of caustic alkalies 
tender silk. Lime-water destroys its luster, and renders 
it brittle. Bleaching-powder affects it, unless the solution 
is very dilute. Sodium or potassium carbonate affects it in 
warm solutions. 

Oxidation of Silk. — Silk is much more easily oxidized 
than wool. 

Potassium bichromate turns it yellow and injures it. 

Potassium permanganate decomposes the fiber if applied 
in excess; in small quantity it turns it brown, and a subse¬ 
quent treatment with sulphurous acid or bisulphite of soda 
bleaches the fiber. 

Bleaching-powder , in very dilute solution, chlores silk, 
and increases its affinity for coloring matters, though not 
to the same extent as wool. In concentrated solutions it 
destroys the fiber. 

Estimation of Silk, Wool, and Cotton. — Silk, cotton, and 
wool can be estimated accurately in fabrics, with the ex¬ 
ception of plush, by the following method : — 

A weighed portion is boiled for io minutes with a i per 
cent solution of hydrochloric acid, washed well, dried at 
ioo° C., and weighed. The acid removes dye and size. 
The weight is the weight of cotton, silk, and wool. 

The silk is dissolved by treating for two minutes with a 
cold solution of nickel hydroxide in ammonia (see Exp. 55), 
the residue digested for two or three minutes in a boiling 
solution of hydrochloric acid (1 per cent), washed, dried 


9 6 


PRINCIPLES OF DYEING 


at ioo° C., and weighed. The residue is the cotton and 
wool. 

The residue is boiled with a 2 per cent solution of soda, 
washed, dried at ioo° C., and weighed. The residue is 
cotton. 

Wild Silks. — Eria silk is found in India; muga silk is 
a native of Assam in Africa; yamomi silk comes from 
Japan; all these come from caterpillars. Sea silk , or 
byssus , is composed of fibers excreted by certain mollusks 
for the purpose of attaching themselves to rocks, and 
comes from Sardinia and Corsica in the Mediterranean 
Sea. 

Tussur silk is the most important of the so-called wild 
silks. It comes from India and China, and is used princi¬ 
pally for the manufacture of artificial sealskins. Tussur 
silk is the product of a caterpillar. 

Under the microscope, tussur silk appears as a flat, 
double fiber, each of which individual fibers can be split 
up into six to eight little fibers or fibrillae by suitable treat¬ 
ment. 

Composition and Properties of Tussur Silk. — Raw tussur 

contains about 5 per cent ash, and about 25 per cent silk 
gum. Its fibroine (fiber constituent) contains less nitrogen 
and more oxygen than ordinary silk. 

Tussur silk is much stiffer than ordinary silk, and has a 
brown color which is difficult to remove. It is more diffi¬ 
cult to dye than ordinary silk. 

Cajistic soda in solution dissolves tussur silk much less 
readily than ordinary silk; concentrated hydrochloric acid 
and chromic acid act in the same way. 


SILK 


97 


Detection of Tussur Silk. — This may be effected as 
follows: — 

(<?) By microscopic examination of the fiber. 

(i b) By boiling with a io per cent solution of caustic 
soda, which dissolves ordinary silk or wool in about io 
minutes. 

(, c ) By concentrated hydrochloric acid, which dissolves 
ordinary silk instantly, tussur silk only slightly even in 
24 hours. 


H 


CHAPTER XI 


OPERATIONS PRELIMINARY TO DYEING-BLEACHING COTTON 

AND LINEN 

As they come into the hands of the dyer, the textile 
fibers are in a more or less impure condition, and as a 
rule, must go through preparatory processes before they 
are ready for the actual dyeing operations. Besides the 
natural impurities, yarns gather dirt and oil from the ma¬ 
chinery, and cloth, in addition, contains the ingredients of 
the size used to strengthen the warp in weaving. 

Cotton contains natural fats and waxes. Woolen yarn 
or cloth usually contains considerable quantities of oil 
added to facilitate the weaving, and silk contains a gum 
which must usually be removed before dyeing. All textile 
fibers contain natural coloring matters to a greater or less 
extent. Cotton warps are sized with tallow, starch, gums, 
China clay, paraffin wax, and other substances. Wool 
warps are sized with glue, for the most part. 

Objects. — The objects of the preliminary operations are 
as follows: — 

(1) To wet the material so that every portion of it will 
be uniformly penetrated by the solution of mordant or dye, 
and not be protected from actual contact with it by bubbles 
of air, etc. 

(2) To remove impurities, such as oil or grease, which 

98 


OPERATIONS PRELIMINARY TO DYEING 


99 


would prevent the mordant or dye from being taken up by 
the fiber. 

(3) To remove natural coloring matters when they 
would interfere with the brilliancy of the color to be pro¬ 
duced. 

In this chapter we will only deal with the processes for 
preparing cotton and linen for dyeing. 

COTTON 

Wetting Out. — When dark shades are to be dyed, or 
light colors of no particular brilliancy, the only preliminary 
operation necessary is wetting out. This only aims at wet¬ 
ting the material evenly, and is accomplished by boiling the 
goods with water, or with water containing a little sodium 
carbonate (soda ash). Sodium carbonate aids in removing 
the natural fats, and also removes any oil stains that may 
be present. Very often, however, it is omitted, and its 
omission is a necessity when dyes are to be used whose 
colors are affected by sodium carbonate, as it is difficult to 
wash the material free from traces of this salt. 

Raw cotton is often not wetted out before dyeing. It is 
usually wetted out in the machine used for dyeing it by 
placing it in the machine and boiling with water until it is 
thoroughly wet. 

Warps and skeins are sometimes wetted out in the dyeing 
machines, but usually in kiers. A kier (Fig. 4) consists of 
a cylindrical wooden or iron vessel (A) provided with a 
top ( 3 ), which can be fastened down tightly. Large 
stones are placed in the bottom of the kier, or there is a 
perforated false bottom. The yarn is packed in around 


100 


PRINCIPLES OF DYEING 


a central iron pipe, the puffer pipe (C), which terminates 
in a hood ( D ), and is so arranged that when a jet of steam 
is sent in at the bottom it forces the water up the pipe and 
showers it over the goods. The liquid then finds its way 
to the bottom of the kier, ready to be forced up again. 
The circulation of the liquid insures thorough treatment of 
every part of the goods. 



Wooden kiers are arranged to work at the ordinary 
atmospheric pressure, or a little above. Iron kiers maybe 
for low pressure (that is, from 5 to 15 pounds), or high 
pressure (working under a pressure of 40 to 50 pounds). 

The construction of the kier varies somewhat according 
to the pressure at which it is to work. 

Bleaching. —The objects of bleaching are as follows : — 

(1) To remove the natural brown coloring matters, which 
have a dulling effect upon bright and brilliant colors, and 





















OPERATIONS PRELIMINARY TO DYEING 


IOI 


whose removal is a necessity for the production of beautiful 
shades. 

(2) To prepare pure white goods for the market (market 
bleach). 

The methods used in bleaching vary extremely, accord¬ 
ing to the material to be bleached, and the effects desired. 
Dark, low-grade cotton naturally requires more vigorous 
treatment or a greater number of operations than high-grade 
cotton. Fine yarns and delicate fabrics must be handled 
more tenderly than coarse materials. Some kinds of dye¬ 
ing require an extremely fine bleach, while a very simple 
bleach suffices for others. 

The number and exact nature of the different bleaching 
operations vary in different mills for the same materials ; 
they also depend somewhat on whether a half bleach, a 
three-quarter, or a full bleach is desired. 

Chemistry of Bleaching. — There are two stages in every 
process of bleaching. The first consists in a treatment 
with alkalies for the removal of natural or acquired fats 
and oils, size, etc., and may be called saponification. The 
second consists in the removal of coloring matters, and is 
called decolonization. 

Saponification.—Animal or vegetable fats are compounds 
of certain organic acids, mainly palmitic, stearic, and oleic 
acids, with glycerol, being in the nature of salts. When 
boiled with sodium carbonate, caustic soda, or lime, the 
fat is decomposed, glycerol and a salt of the fatty acid 
being formed. 

C 3 H 5 (C 16 H 31 0 2 ) 3 + 3NaOH = C 3 H 5 (OH) 3 + 3 NaC 16 H 31 0 2 . 

Fat (palmitin). Glycerol. Sodium palmitate. 


102 


PRINCIPLES OF DYEING 


The sodium or potassium salts of these acids is ordinary 
soap, and the process of making them is called saponifica¬ 
tion. Cotton wax, mineral lubricating oils, and paraffin 
wax are not saponified or made soluble in water by alkalies. 
A soap solution, however, has the power of removing these 
substances in the form of minute drops suspended in the 
liquid, that is, as an emulsion. But if present in too large 
quantity, mineral lubricating oil or paraffin wax are not 
removed, and the result is a stain in the finished goods. 

Methods.—There are two general methods of saponifi¬ 
cation : — 

(1) The saponification is accomplished directly by boil¬ 
ing the cotton with solutions of caustic soda, or sodium 
carbonate, sometimes with addition of resin. 

(2) This method is applied to cloth only. The saponi¬ 
fication is accomplished in several stages : —• 

(a) Boiling with lime-water under pressure, an insoluble 
lime soap being formed. 

(b) The lime soap is decomposed by an acid : — 

CaAc 2 + 2 HC 1 = CaCl 2 + 2 HAc. 

(c) Boiling with resin soap under pressure, and 

(a) Boiling with soda ash under pressure. 

These last two operations remove the fatty acids, dis¬ 
solving them in the form of their sodium salts. The resin 
soap probably aids in emulsifying mineral oil and waxes. 

Decolorization. — After grease, waxes, etc., have been 
removed by saponification, the cotton still retains a light 
brown color. The second stage in bleaching consists in 
the oxidation of the color. The success of this operation 


OPERATIONS PRELIMINARY TO DYEING 


103 


depends upon the thoroughness with which the preceding 
operations of saponification have been carried out. The 
color may be partly or completely removed, according as a 
partial bleach or a full bleach is desired. 

The oxidizing agents used in bleaching are: — 

(1) Chloride of lime, or bleaching-powder, and sodium 
hypochlorite. 

(2) Potassium permanganate. 

(3) Hydrogen peroxide. 

Decolorizing Agents. — Bleaching-powder (Ca(OCl) 2 ) is a 
white powder with the odor of hypochlorous acid. It is sol¬ 
uble in twenty times its weight of water, but always leaves 
some undissolved residue. When treated with an acid, as 
sulphuric or hydrochloric acid, it gives up all its chlorine. 
Thus, with hydrochloric acid the reaction is as follows : — 

Ca(OCl) 2 + 2 HC 1 = CaCl 2 + 2 HCIO, 

2 HC 1 + 2 HCIO = 2 H 2 0 + 2 Cl 2 . 

Experiment 56. — Add hydrochloric acid to a little bleaching- 
powder in a test-tube. What is given off? Write reaction. 

Color 500 cc. water faintly with a little aniline blue, and add 
bleaching-powder solution. What happens ? Repeat, using fuch- 
sine ; using methylene blue. 

In bleaching, bleaching-powder is aided to a great ex¬ 
tent by the carbonic acid of the air, which liberates hypo- 
chlorous acid, and the latter acts readily upon the color to 
oxidize it: — 

Ca(OCl) 2 + H 2 0 + C 0 2 = CaC 0 3 + 2 HCIO, 

HCIO = HC 1 + O. 

The hydrochloric acid acts upon the chloride of lime, 
liberating more hypochlorous acid. 


104 


PRINCIPLES OF DYEING 


After the goods have been treated with bleaching-pow- 
der, they are washed and treated with dilute acid, to com¬ 
plete the decomposition of the bleaching-powder, and to 
dissolve calcium carbonate. Sulphuric acid, hydrochloric 
acid, or acetic acid may be used. When mineral acids are 
used, the fiber must be washed very carefully to prevent 
tendering, a precaution not necessary for acetic acid. 

Antichlorine compounds, consisting usually of a solution 
• of sodium acid sulphite (NaHS 0 3 ), are often used to remove 
all traces of chlorine from the fabric. 

Experiment 57. — Bleach two skeins of cotton yarn, regular 
yarn, and a low-grade, dark yarn as follows : — 

(1) Saponification. Boil for half an hour in 500 or 600 cc. 
water with 4 per cent sodium carbonate. While boiling, prepare 
the bleaching-powder solution for (2). What is the color of the 
solution of sodium carbonate after the yarn has been boiled in it ? 
Is the yarn darker or lighter than before ? 

(2) Decolorization. Grind 5 g. bleaching-powder with 20 cc. 
water in a mortar, pour into 500 cc. water, and wash the contents 
of the mortar into it. Stir well, and allow to settle ; the liquid will 
not become perfectly clear. 

Pour the liquid over the skeins, work for 5 minutes, and allow 
to stand half an hour. Without washing, enter the yarn in a bath 
of 3 cc. concentrated hydrochloric acid in 500 cc. water. Enter 
the yarn, and work 5 minutes. Wash well and dry. What is the 
difference in color between the two skeins ? 

Sodium hypochlorite (NaCIO) is sometimes used for 
bleaching in place of bleaching-powder. It is prepared 
by treating a solution of bleaching-powder with the proper 
quantity of sodium carbonate : — 

Ca(OCl) 2 + Na 2 C 0 3 = CaC 0 3 4- 2 NaCIO. 


OPERATIONS PRELIMINARY TO DYEING 


105 


The precipitated calcium carbonate is allowed to settle, 
and the clear solution drawn off. Its properties are simi¬ 
lar to those of bleaching-powder. 

Sodium hypochlorite is the active agent in electrolytic 
bleaching processes. It is prepared by passing an electric 
current through a solution of common salt, under suitable 
conditions. 

Hydrogen peroxide (H 2 0 2 ) is too expensive for use in 
cotton bleaching, except in rare cases. It is applied to 
cotton by a method similar to that used for wool (Chapter 
XII). 

Potassium Permanganate. — This salt is sometimes used 
in cotton bleaching in neutral or acid solution. The reac¬ 
tion in acid solution is as follows : — 

2 KMn 0 4 + 3 H 2 S 0 4 = K 2 S 0 4 + 2 MnS 0 4 + 3 H 2 0 + 5 O. 

In neutral solution, manganese dioxide is precipitated on 
the material. 

2 KMn 0 4 + H 2 0 = 2 KOH -f 2 Mn 0 2 + 3 O. 

The manganese dioxide, which imparts a brown color to 
the goods, is removed by treatment with sulphites. 

Mn 0 2 +H 2 S 0 3 =MnS 0 4 +H 2 0 . 

Oxycellulose. — During the process of bleaching by 
bleaching-powder or potassium permanganate, the cellulose 
probably undergoes a slight oxidation to oxycellulose, but 
under proper conditions no injurious action takes place. 
Under certain conditions oxidation may go too far, with 
the result that the fiber is weakened, or tendered. This 
action has already been referred to (see Tendering of 
Cellulose). 


106 PRINCIPLES OF DYEING 

Bleaching Loose Cotton. — Loose cotton is sometimes 
bleached. The operations may be conducted in the appa¬ 
ratus for dyeing loose cotton (Chapter XIII), or in wooden 
vats provided with a false bottom, the cotton being stirred 
with poles. 

The methods vary ; the following is an example : — 

(1) Ley Boil. — The cotton is boiled with sufficient wa¬ 
ter, and 2 to 3 per cent of its weight of sodium carbonate. 

(2) Chemicking . — The cotton is saturated with a clear 
solution of bleaching-powder at | to 2° Tw. ; after an hour 
or more the liquid is drawn off, and the moist cotton al¬ 
lowed to remain undisturbed for some hours. It is then 
washed. 

(3) Souring. —The cotton is treated with acid at J to i° 
Tw. washed, hydro-extracted, and dried. 

Yarn Bleaching. — Yarn is bleached as warps or skeins, 
more rarely on the cop; cop bleaching requires special 
apparatus. 

The series of operations is as follows: (1) ley boil, and 
wash ; (2) chemic, and wash ; (3) sour, and wash. 

Ley Boil. —The yarn is boiled for 6 to 10 hours with 3 
to 6 per cent sodium carbonate (soda ash), or with caustic 
soda, or a mixture of the two. Caustic soda saponifies the 
cotton oil more readily than sodium carbonate. The boil¬ 
ing is conducted in a high or low pressure kier, and the 
duration of the boil depends on the pressure in the kier. 
With a high-pressure kier, the operation requires less time. 

Skeins are linked into chains 6 feet long or longer, or 
they may be left separate if a skein-washing machine is at 
hand. Warps, if long, are doubled two, three, or four times 


OPERATIONS PRELIMINARY TO DYEING 107 

to reduce their length, or are linked up in slip-knot forma¬ 
tion,— their ends are tied together to prevent entanglement. 
The yarn is packed evenly in the kier, so that the solution 
will circulate through it, and not through channels between 
the bundles of yarn. It is covered with coarse linen cloth, 
and weighted down with beams. Sufficient water must be 
used to cover the goods completely and insure that they do 
not come in contact with the air during the operation, which 
would tender them by oxidation. Iron kiers should be kept 
covered with lime, as the bare iron will produce stains on 
the yarn. Hard water sometimes produces stains, due to 
the formation of a brown insoluble calcium salt of cotton 
oil, which is difficult to remove in bleaching. 

After boiling, the yarn is washed partly in the kier, and 
the washing is completed in washing machines, described 
later. It is then hydro-extracted, and chemicked. 

A second ley boil is often given. 

Chemicking. —The success of this operation depends on 
the thoroughness of the ley boil. The yarn is treated with 
a solution of bleaching-powder of J to i° Tw., according to 
its fineness. Some bleachers allow it to remain in this 
liquid 3 or 4 hours, and then remove and sour, while others 
draw off the solution and allow the yarn to lie exposed to 
the air for some time before souring. For very fine yarns, 
which are easily tendered by a bleach liquor which is too 
strong, the strength of the liquid should be determined by 
titration. The method is given later. 

The chemicking, souring, and washing may be conducted 
(Fig. 5) in a stone or wooden cistern (A), provided with a 
false bottom ( 3 ), into which the yarn is laid or packed 
evenly so as to secure an even circulation. The liquid with 


io8 


PRINCIPLES OF DYEING 


which the yarn is to be treated is raised by means of a pump 
(£7) from a well below the floor into a perforated wooden 
tray ( D ), which showers it over the goods. It percolates 

through the goods, 
accumulates below 
the false bottom, 
and flows back into 
the cistern. A cir¬ 
culation of liquid is 
thus kept up dur¬ 
ing the entire opera¬ 
tion. The strength 
of the liquors must 
be restored from 
time to time. This 
apparatus is called 
the sieve, and the 
operations chemick- 
ing under sieve , 
etc. The chemic 
and acid act upon 
the pump, neces- 

FlG. 5. — Bleaching under sieve. sitating frequent 

repairs. 

The chemicking may also take place in plain wooden 
vats or cisterns, the yarn being thrown into the liquid. At 
the end of the operation, the bleach liquor is, as a rule, only 
half exhausted, and is pumped off into an empty cistern, and 
used again after its strength has been restored. 

Souring. — Sulphuric, hydrochloric, or acetic acid of from 
1 to 2° Tw. are used. The yarn is then carefully washed. 






















OPERATIONS PRELIMINARY TO DYEING 109 

Cop Bleaching. — In cop bleaching, the hot alkaline liquor 
and the cold bleaching liquors are forced through the cop 
by apparatus described under cop dyeing. Sodium hypo¬ 
chlorite is usually used in place of calcium hypochlorite. 

Preparing the Chemic. — To prepare the bleaching liquid, 
a sufficient quantity of chloride of lime is thoroughly mixed 
with water — at least three gallons of water per pound of 
bleaching-powder — in wooden or stone vessels, and the 
solution allowed to settle. For 1000 pounds yarn, about 
30 pounds bleaching-powder are required. The clear solu¬ 
tion is drawn off and diluted to the desired strength. 

For dissolving the chloride of lime a special apparatus is 
in use. It consists of a square cast-iron, lead-lined vessel, 
containing a wrought-iron perforated drum, also lined with 
lead. After the bleaching-powder has been placed in the 
drum with sufficient water, it is revolved until solution is 
complete. The solution is drawn off by means of a tap, 
placed at a sufficient distance from the bottom to avoid 
disturbing the sediment. 

Control of the Chemic. — The chemic, sour, and many 
other solutions of the dyer are made up approximately to 
some desired strength by the aid of hydrometers, since the 
density of a solution varies with its strength. 

The hydrometer is an instrument to measure the density 
of a liquid, by being placed in it. It is constructed on the 
principle that a floating body will sink in a liquid until it 
has displaced its own weight of the liquid. The instrument 
consists of a glass bulb connected with a graduated stem. 
Below the bulb is a smaller bulb of mercury to hold the 
instrument upright. The instrument is placed in the liquid 


110 


PRINCIPLES OF DYEING 


to be tested, and the reading at the point to which it sinks 
gives the density of the liquid. 

Hydrometers are graduated in several ways, the most 
important being as follows : — 

(1) Specific Gravity Hydrometers .—The scale on the 
stem of this instrument shows the specific gravity of the 
liquid. 

(2) Twaddle Hydrometer. —The scale is so divided that 
degrees Twaddle can be converted into specific gravity by 
multiplying by 5, adding 1000, and dividing by 1000. 

For example, io° Tw. = 1.050 specific gravity. 

(3) Bannie Hydrometer .—This is often used. There is 
no simple relation between degrees Be. and specific gravity. 
A table can be used for converting them. 

The indications of a hydrometer are sometimes not 
delicate enough, and in other cases its indications are 
misleading. In such cases recourse must be had to chemi¬ 
cal methods. 

Titration of the Chemic. — The strength of a solution of 
bleaching-powder is reduced when it is used, without a corre¬ 
sponding reduction in its density. To ascertain the strength 
of bleach liquors which have been used, so that they can be 
restored to the proper strength, a portion must be withdrawn 
and titrated according to the following method: — 

4-95 g- °f finely powdered arsenious oxide are dissolved 
in 15 cc. glycerol with the aid of a gentle heat, and the 
solution diluted to a liter. 25 cc. of the solution are placed 
in a beaker, diluted to 100 cc. with water, and 1 cc. of a 
solution of indigo carmine added. Before bleaching, a 
sample of the bleach liquor is run slowly into this solution 


OPERATIONS PRELIMINARY TO DYEING 


11 1 


from a burette until its color is just discharged. After 
bleaching, the operation is repeated. 

The volume of the bleaching liquid required to effect 
the decolorization varies with its strength. If 20 cc. are 
required before bleaching, and 40 cc. afterward, the 
strength of the liquid has decreased to f# or \ of its 
former power, and its strength can be restored by adding 
one-half the quantity of the strong solution of chloride of 
lime used in preparing the bleaching liquid at first. If 20 
cc. are required before, and 60 cc. afterward, to decolorize 
the solution of indigo carmine and arsenious acid, the 
bleach liquor is only or J as strong as it was at first. 

The indigo carmine solution is prepared by dissolving 
1 g. indigo carmine in 500 cc. water. 

When fine yarns or delicate fabrics are to be bleached, 
the strength of the bleach liquor is best determined by a 
chemical method instead of by the hydrometer, since too 
strong a solution may cause tendering. The method just 
described may be used to test the strength of the solution. 

Control of the Sour. — After once using, the density of 
the sour is no indication as to its strength. Its strength 
must be determined by titration, as is the case with the 
bleach liquor, and it can then be restored to the required 
degree of activity by the addition of fresh quantities of 
acid. The method for dye-house work is as follows : — 

Dissolve 4 g. of chemically pure caustic soda in 1000 cc. 
water. Dilute 20 cc. of the sour to 100 cc., add a few 
drops of a dilute solution of methyl orange, and add the 
caustic-soda solution slowly from a burette until the color 
of the solution just changes. After using, the liquid can 


I 12 


PRINCIPLES OF DYEING 


be titrated again and made up to its original strength by 
the addition of acid. The solution of caustic soda should 
be protected from the air. 

Cloth Bleaching. — Three essentially different processes 
of bleaching cloth are in use, namely, the market or white 
bleach, the Turkey-red bleach, and the printer’s bleach. 

The object of the market bleach is to produce a white 
which will please the eye of the customer. 

The Turkey-red bleach prepares the goods for dyeing or 
printing with alizarine, or the production of Turkey-red. 

The printeds bleach is preliminary to calico printing. 
It is the most perfect of the three, as every impurity which 
would attract dye must be removed. 

Printers Bleach. — The general outline of the printer’s 
bleach is as follows: the cloth passes through most of the 
operations in the form of a rope, the different pieces being 
sewed together, end to end. 

(1) Singeing. — The loose fibers are burned off by pass¬ 
ing the cloth over a row of Bunsen burner flames, or over 
a heated metal plate or roller. 

(2) Singeing Wash. —The cloth is washed to remove as 
much of the loose charred fibers as possible. In the wash¬ 
ing machine (Fig. 6) the cloth passes between squeezing 
rollers (A), then under another roller in a trough of water 
(. B ), again through the squeeze rollers (A), and through the 
water, and so on a number of times until it passes away at 
the end. Clean water constantly flows into the trough. 

(3) Lime Boil. — The cloth is limed with milk of lime, in 
a machine similar to the washing machine though con¬ 
structed somewhat differently, run into an iron kier, cov- 



OPERATIONS PRELIMINARY TO DYEING I I 3 

ered with water, and boiled under 15 to 50 pounds’ pressure 
for 6 to 10 hours. From 5 to 7 pounds of lime are used 


per 100 pounds of goods. When the lime-water is run 
off, the kier is filled as rapidly as possible with cold water 
1 


Fig. 6. — Cloth washing machine, 














































































































































PRINCIPLES OF DYEING 


114 

to prevent the lime from drying where it is in contact 
with the hot sides of the kier, which will cause tendering 
or brown stripes on the goods. 

(4) Lime or Gray Sour. — The cloth passes through 
hydrochloric acid of 2° Tw. in a machine 'similar to the 
washing machine, the sour being kept to a uniform strength 
by titration of the solution and additions of acid from time 
to time. The cloth is then washed in a washing machine. 

(5) Ley Boil. —The cloth is boiled in kiers with a solu¬ 
tion of soda ash (1.7 to 3.0 per cent of the weight of the 
cotton), or caustic soda (1.2 to 1.5 per cent), for 3 to 5 
hours in a high-pressure kier, and washed. 

(6) Resin Boil. —• The cloth is boiled with resin soap 
and caustic soda for 7 to 12 hours. Resin soap is pre¬ 
pared by boiling resin in a solution of sodium carbonate of 
about 20° Tw. until it dissolves. Resin floats on a solu¬ 
tion of this strength, and dissolves more quickly than in a 
more dilute solution. 

(7) Chernicking. — The cloth passes through a solution 
of bleaching-powder of J to i° Tw., in a machine similar 
to the washing machine, is piled up in a heap, and allowed 
to lie over night. It is generally washed before souring. 

(8) White Sour. — The goods are passed through hydro¬ 
chloric, sulphuric, or acetic acid at i° to 2° Tw. 

(9) Filial Washing. — The machine already described 
may be used. A more effective machine is the square 
beater washing machine (Fig. 7). The pieces, stitched 
together, pass in the form of a rope between two squeeze 
rollers (A), then under a square beater (A), directly beneath 
in the water, along under the surface of the water to 
another roller ( C ), and back to the squeeze rollers (A). 


OPERATIONS PRELIMINARY TO DYEING I I 5 

The pieces follow the same course over and over again in 
a spiral direction, until they leave the machine. In pass¬ 
ing the square beating roller, which revolves in a direction 
opposite to that followed by the pieces, the cloth opens 
out from the rope form to almost its full width, and at the 
same time receives a flapping motion as it passes along 
the surface of the water. 



Pig. 7. — Square beater washing machine (Mather and Platt). 

Market Bleach. — The methods and machinery adopted 
for the market bleach depend to a great extent on the 
nature of the goods. Ordinary cloth is made into the rope 
form, and the same machines may be used as in the printer’s 
bleach. Light fabrics are dealt with in the form of bundles 
or lumps, and the chemicking and souring are done in cis¬ 
terns as in yarn bleaching. 

For washing light fabrics, the dash wheel may be used. 
The goods are put in the compartments of a drum, which 

























































PRINCIPLES OF DYEING 


I 16 

is caused to revolve, and at the same time a current of 
water flows in and washes the goods. The speed of the 
drum should be such that the goods are thrown from side 
to side of the compartments. A similar machine is used 
in leather dyeing. 

For the market bleach, singeing is generally omitted, 
soda ash is substituted for resin soap in the resin boil, and 
many dyers omit the lime boil. After bleaching, the 
goods are blued , i.e. passed through water containing a 
small quantity of a blue coloring matter, which neutral¬ 
izes a slight yellow tinge of the goods. 

Turkey-red Bleach. — For goods to be dyed Turkey-red, 
bleaching with chloride of lime is generally omitted. The 
goods are boiled with water, given one or two ley boils, 
soured with sulphuric acid, washed, and dried. 

Defects in Bleached Goods. — Defects may be due to iron 
stains, oil stains, and oxidation of the fiber. 

Iron stains appear as red spots, and are apt to be pro¬ 
duced when rusty machinery comes in contact with the 
goods, or when the iron kier is not completely coated with 
lime. They may also be produced by the use of water 
containing too much iron, and by the dropping on the cot¬ 
ton of lubricating oil charged with iron derived from the 
wear of the machinery. Iron stains are hard to remove. 
They may often be removed by saturating the spot with 
strong hydrochloric acid, and washing. 

Oil stains occur as bright yellow stains in various shapes, 
and often do not appear until some time after the goods 
have been sent out. They may be due to the use of 
paraffin wax in sizing the warps, or to the use of mineral 


OPERATIONS PRELIMINARY TO DYEING Iiy 

oils for lubricating, since lubricating oil very often gets 
on the goods. The paraffin wax or mineral oil cannot 
be saponified, and can only be removed when properly 
mixed with tallow or other fat, or with animal or vegetable 
oil, as the case may be. If the paraffin is not removed, 
when the goods are chemicked the paraffin takes up chlo¬ 
rine, forming compounds which turn yellow when exposed 
to light and air. Such oil stains may be removed by satu¬ 
rating the spots with a little olive oil, and boiling in weak 
caustic soda after the oil has soaked in thoroughly. 

Injury through oxidation of the fiber, appearing as ten¬ 
dering in spots or stripes, may be caused : — 

During the Icy boil , by the goods coming in contact with 
the air. 

During the lime boil, by the fabric coming in contact 
with the air, or by lime being dried upon it by the hot 
sides of the kier. 

During the bleaching, by the use of too strong solutions 
of bleaching-powder, or by particles of undissolved bleach- 
ing-powder coming in contact with the material. 

Injury by over-oxidation may be detected by means of 
methylene blue (Exp. 44). 

Acids may cause tendering, if at any time the material 
is allowed to dry while it contains even a trace of sulphuric 
or hydrochloric acid. 

Other Bleaching Processes. — There are bleaching pro¬ 
cesses in which the action of the bleach liquor is acceler¬ 
ated by the addition of acetic acid to the solution, which 
liberates hypochlorous acid, or by passing the damp goods 
through a chamber containing carbon dioxide. 


118 


PRINCIPLES OF DYEING 


In electrolytic bleaching processes, the bleach liquor is 
prepared by the electrolysis of solutions of sodium chloride, 
or of sodium and magnesium chlorides. 

LINEN 

The raw linen fiber contains a much larger amount of 
foreign substances than cotton. While ordinary cotton 
loses only about 5 per cent, linen loses from 25 to 30 per 
cent in weight during bleaching, the loss consisting in wax¬ 
like substances and pectic matters. The bleaching of 
linen is a longer and more tedious process than cotton 
bleaching; while the process, in general, is similar, weaker 
reagents must be used, as a severe treatment would result 
either in a tendering of the fiber, or in causing it to be 
permanently yellow (“setting” the color). Some of the 
operations must be repeated several times before a satis¬ 
factory white is obtained. 

Linen Yarn.—The following is an example of a linen 
bleach: — 

(1) Ley boil , with sodium carbonate in low-pressure 
kiers, and wash. 

(2) Chemicking. — The yarn is reeled for an hour in chlo¬ 
ride of lime solution at Tw. In reeling the skeins are 
hung on poles which receive an alternate backward and 
forward rotation, and only a part of the yarn is immersed 
in the liquid. Wash. 

(3) Sour with sulphuric acid, and wash. 

(4) Scald by boiling with soda ash. Wash. 

(5) Chemic as before. Wash. 

(6) Sour , and wash. 


OPERATIONS PRELIMINARY TO DYEING 


119 

This gives a half bleach. For a three-quarter bleach, 
the yarn is (7) scalded , (8) grassed , by exposure in fields 
for about a week, (9) chemicked , (10) soured , and washed. 
For a full bleach the latter operations are repeated two or 
three times. The strength of linen yarn decreases the 
more thoroughly it is bleached. 

Hydrogen peroxide will probably bleach linen with less 
weakening. The methods are the same as for wool. 

Linen Cloth. — An outline for a linen-cloth bleach is as 
follows: (1) lime boil; (2) sour; (3) ley boil; (4) ley 
boil; (5) grass; (6) chemic; (7) sour; (8) scald; (9) 
grass; (10) chemic; (11) rub on boards, to remove black 
specks; (12) grass; (13) chemic; (14) sour. 

Jute Bleaching.—Jute may be bleached by treatment 
first with a warm solution of bleaching-powder, and then, 
after washing, with dilute sulphuric acid. The material is 
then washed. If a lighter color is desired, the treatment 
is repeated with weaker solutions. 

Another method is as follows : Pass the goods through a 
bath of 1 per cent silicate of soda, heated to about 70° C., 
wash, and then immerse in a bath of sodium hypochlorite 
containing not more than 1 per cent of available chlorine. 
The duration of the immersion depends on the grade of 
jute to be bleached ; wash, and pass through hydrochloric 
acid at |° Tw., and wash thoroughly. A still lighter color 
is obtained if the goods are next passed through a bath 
containing about 2 per cent sulphurous acid, free, or in 
the form of sodium bisulphite. 


CHAPTER XII 


WOOL AND SILK SCOURING AND BLEACHING 

Washing Loose Wool. — Loose wool usually contains from 
30 to 80 per cent dirt, suint, and yolk. The thorough re¬ 
moval of these impurities is absolutely necessary before the 
wool can be made into yarn, since it is extremely difficult 
to remove them from yarn. Imperfect scouring leads to 
defects in dyeing. The operation of zvasJiiug or scouring is 
very simple. The wool is washed with a warm solution of 
soap, which dissolves the fats and carries off the waxes in 
the emulsified condition. Three successive soap-baths are 
usually used. The wool is rinsed, squeezed, and dried. 

Methods and Machinery. —The best results are obtained 
with a neutral, soft soap, and temperatures not above 35 0 C. 
Too high a temperature causes the wool to be harsh. For 
low-grade wool a cheap soap is often used, sometimes with 
the addition of sodium carbonate or sodium silicate; or 
sodium carbonate with no soap. The amounts of soap 
or soap and soda to be used depend upon the condition of 
the wool. Pitchy wool requires more than ordinary wool. 

The wool may be washed in a wooden vat provided with 
a false bottom. It is stirred with poles. One type of 
machine consists of a rectangular iron tank, provided with 
a false bottom and an automatic arrangement of forks or 
prongs by which the wool is made to pass slowly from en¬ 
trance to delivery end. The forks are attached to a frame, 


120 


WOOL AND SILK SCOURING AND BLEACHING 


121 


which makes a forward stroke in the water, then a back¬ 
ward stroke in the air, and so on ; thus setting up a circu¬ 
lation of suds which carries the wool forward. At the 
delivery end the wool is squeezed by a pair of squeezing 
rollers. The dirt collects below the false bottom of the 
tank. 

Three of these machines may be used; in order to save 
soap, the suds from the squeezing rollers on the last ma¬ 
chine, which are comparatively clean, are used in the sec¬ 
ond one, and then in the first, when they are allowed to 
run off. 

Drying machines used are similar to those used for dry¬ 
ing cotton (Chapter XIII). Too high a temperature in 
drying injures the quality of the wool. 

Soaps. — Soaps are made by boiling fats or oils with 
caustic soda or caustic potash, or their carbonates. The 
best soap for wool washing is a soft soap made with 
potash. Such a soap is readily soluble in water, and 
easily washed out. Soap which contains resin should be 
avoided, as it gives a disagreeable odor, makes the fiber 
yellow and sticky, and may give rise to uneven dyeing 
afterward, since the resin is difficult to remove by wash¬ 
ing. Soap containing free caustic alkali (sodium or po¬ 
tassium hydroxides) tenders the wool, but this can be 
prevented by the addition of ammonium carbonate or 
some other ammonium salt, which reacts with the alkali 
to form ammonium hydroxide. 

By-products. — The waste water from wool washing con¬ 
tains potassium carbonate, wool grease, and soap grease, 
which it often pays to recover. 


122 


PRINCIPLES OF DYEING 


Potassium Carbonate. — From i to 8 per cent of potassium 
carbonate (average about 3J per cent) can be recovered 
from raw wool. When this is to be recovered, the raw 
wool is extracted with warm water before being scoured 
with soap. The watery extracts are evaporated to dry¬ 
ness, and calcined in specially constructed furnaces. In 
extracting with water, five or six vats may be used, so 
arranged that water can flow naturally from the first to the 
second, and so on. The raw wool in baskets is placed, first 
in the dirty water in the bottom vat; after a short time the 
baskets are transferred to the next vat, a fresh lot being 
placed in the first, and so on until the wool passes through 
the clean water in the top vat. As the water passes down, 
it becomes more and more impure. This is called the 
counter-current system, and economizes water, and, neces¬ 
sarily, fuel for evaporating it. A similar system is em¬ 
ployed in the hank yarn-washing machine (Chapter XIII). 

Wool grease .—The fat from the wool and the soap in 
the water from wool washing may also be recovered. The 
waste water is collected in large tanks and the dirt allowed 
to settle. The water is then treated with sulphuric acid, 
which decomposes the soap, and the fatty acids rise to the 
surface, bringing the wool grease with them. The water is 
strained off through canvas filters, and the grease purified 
by pressing it through sheets of canvas, melting it, and 
allowing the impurities to settle. It is used as a lubricant, 
and in cold climates for smearing sheep. 

Other Methods of Wool Washing.—Treatment of the 
wool with a volatile solvent, to remove wool grease, and 
then with water to remove suint, has been tried, but finds 


WOOL AND SILK SCOURING AND BLEACHING 123 

little application on a large scale. The solvents used are 
carbon bisulphide, benzene, toluene, and petroleum ether. 
The wool grease is recovered by distilling off the solvent, 
and the latter is used over again. 

Yarn Scouring. — Woolen and worsted yarns usually 
contain 2 to 6 per cent oil added to prevent the yarn from 
breaking during spinning. Shoddy yarns may contain 15 
per cent oil. The oil is usually removed by scouring before 
dyeing or bleaching; with cheap blacks the scouring is 
sometimes omitted. 

Some wool yarns curl when wetted, and before scouring, 
such yarns must be stretched to prevent them from becom¬ 
ing entangled during the operation. The yarns are tightly 
stretched in a frame between pairs of iron rods and im¬ 
mersed in boiling water for half an hour, removed, and al¬ 
lowed to cool. The skeins then are turned halfway around 
and again treated with boiling water. This process takes 
advantage of the plasticity of wool at high temperatures. 

Methods and Machinery. — The yarn scouring is best 
done in a solution of soap, or of soap and soda heated to 
35~45°C. The procedure varies in different works. For 
the best grades of wool only a good soap is used. The 
methods are as follows : — 

(1) The hanks are hung on sticks as in skein dyeing and 
turned two or three times in the soap solution contained 
in an ordinary dye-vat, about a hundred pounds being 
scoured at a time. They are washed in the same way and 
hydro-extracted. 

(2) A hank is placed in the warm soap solution, allowed 
to soak while a second is being turned, is turned, and thrown 


124 


PRINCIPLES OF DYEING 


on a traveling apron which carries it between a pair of 
squeezing rollers. It is then washed, squeezed, and dried. 

(3) The hanks are tied loosely together, end to end, to 
form an endless belt, which is caused to circulate through 
the soap bath by means of squeeze rollers. The machine 
resembles the dolly. 

By-products. — The wash waters from yarns may be 
treated like the water from loose wool to recover the soap 
grease. 

Cloth Scouring. — In the manufacture of plain goods it 
is not usual to scour yarn before weaving. For common 

black or heavy woolens, 
the cloth is frequently mor¬ 
danted and dyed without 
scouring. Low-grade black 
worsteds are simply washed 
in soda. For better-class 
blacks, and for pieces to be 
dyed in colors, the material 
is scoured in soap or soap 
and soda. 

There are two kinds of 
scouring machines. In the 
dolly (Fig. 8) the pieces, 
sewn together to form an 
endless chain, are made to 
Fig. 8 . —Cloth-scouring machine. pass in the form of a loose 

rope through the vessel 
(A), which contains the solution of soap, and between 
two wooden rollers (bowls) (B). The bowls draw the 








WOOL AND SILK SCOURING AND BLEACHING 125 

pieces through the liquid, at the same time expressing 
the dirty wash water from them, which flows off in' a 
trough (C) below the lower bowl. 

The “ broad washing ” machine is similar to the dolly, 
except that the pieces pass through the rollers in the open 
width. It is used for pieces which are liable to crimp or 
crease if scoured in the rope form. 

Crabbing. —Wool cloth made from mixtures of different 
classes of wool and goods of mixed cotton and wool become 
uneven when brought in contact with water on account of 
the different degree of contraction between the two fibers. 
To prevent this, they must be crabbed before dyeing. 

The cloth passes at full breadth, and under considerable 
tension, through boiling water, is wound tightly on a roller, 
and allowed to cool. The operation is repeated. The 
cloth is then wound tightly on a perforated iron cylinder, 
into which steam is admitted. After cooling, the cloth is 
wound on a second cylinder, and the operation repeated, 
so that all parts of the cloth will be equally subjected to the 
action of the steam. 

Wool Bleaching. — The bleaching of wool is an entirely 
different process from the bleaching of cotton and linen. 
Wool would be completely destroyed in any process of 
cotton bleaching. In bleaching, the wool is first scoured 
carefully. It can then be bleached in two ways: (i)by 
sulphurous acid ; (2) by hydrogen peroxide. 

Sulphur Bleach. — In wool bleaching sulphurous acid 
converts the coloring matter to a colorless body, either by 
reducing it or by uniting with it directly. The change is 
not permanent, for bleached wool treated with alkaline sub- 


126 


PRINCIPLES OF DYEING 


stances, like soap or soda, becomes yellow again. The 
bleaching is effected by stoving , or by the use of solutions 
of sulphurous acid or sodium bisulphite. 

Stoving .—The stove consists of a small brick or stone 

<D 

chamber lined with wood, which can be closed air-tight. 
All iron and other metals must be excluded, as they are 
soon destroyed. Skeins , in a damp condition, are hung on 
wooden rods. About 6 pounds sulphur per ioo pounds 
of wool are placed in the chamber, and set on fire, and the 
chamber is closed. After being exposed to the sulphur di¬ 
oxide 6 or 8 hours, or over night, the skeins are removed 
and aired. Pieces may be bleached in a continuous form of 
apparatus. They are sewn together, and pass through a 
narrow slit in the side of the stove, then many times up and 
down over wooden rollers, and finally out again. 

Hydrogen Peroxide Bleach. — Hydrogen peroxide is com¬ 
ing into favor as a bleaching agent for wool. It oxidizes 
and destroys the coloring matter, and produces a permanent 
bleach. The bleaching bath may be prepared from com¬ 
mercial hydrogen peroxide, or from sodium peroxide. 

Hydrogen peroxide , H 2 0 2 , comes on the market as a 
3 per cent solution in water. It may be adulterated with 
oxalic acid. 

The bleaching bath is prepared by diluting the solution 
with 5 to 15 volumes of water, and then making alkaline 
with ammonia or water-glass (sodium silicate). Ammonia 
is best, as sodium silicate is said to give the wool a harsh 
feel. 

The more alkaline the bath, the quicker its action; but 
oxygen is evolved from a bath which is too alkaline. The 


WOOL AND SILK SCOURING AND BLEACHING 12y 

wool is entered into the cold solution, and the bath is gradu¬ 
ally heated to 54 0 C. Lead pipes should be used for heat¬ 
ing ; and iron and other metals in any form should not be 
present in the bath, as they cause decomposition of the 
hydrogen peroxide. The bleaching lasts from 3 to 8 hours. 
The wool is then soured with a per cent solution of 
hydrochloric or sulphuric acid, and rinsed. If the bath is 
heated to a higher temperature, bleaching takes place more 
rapidly, but more hydrogen peroxide is consumed. 

Sodium Pei'oxide , Na 2 0 2 , is a pale yellow powder, which 
is decomposed if exposed to the air, being converted into 
sodium carbonate. It should be kept in well-closed 
vessels. 

When treated with water, it yields hydrogen peroxide : — 
Na 2 0 2 4- 2 H 2 0 = 2 NaOH -f- H 2 0 2 . 

But in the presence of the sodium hydroxide, the hydro¬ 
gen peroxide is decomposed almost as rapidly as formed: — 

H 2 0 2 = H 2 0 + O. 

If sulphuric acid or some other acid is present, decom¬ 
position does not take place : — 

Na 2 0 2 + H 2 S 0 4 = Na 2 S 0 4 -f H 2 0 2 . 

Sodium peroxide is liable to set fire to paper or other 
combustible matter with which it comes in contact. It 
is 13 or 14 times as strong as commercial hydrogen 
peroxide. 

For bleaching with sodium peroxide , sulphuric acid is first 
added to the bath, — from 7 to 14 pounds per 100 gallons 
of water. Sodium peroxide (5 to 10 lb.) is next added, 
with thorough stirring, until litmus paper is just turned 


128 


PRINCIPLES OF DYEING 


blue, and the bath is then made acid with sulphuric acid. 
Ammonia or sodium silicate is then added, until the litmus 
paper begins to turn blue again. If the bath contains any 
sodium hydroxide, or is too strongly alkaline, the wool will 
acquire a yellow tint, which it is afterward next to impos¬ 
sible to bleach out. The bleaching is conducted as with 
hydrogen peroxide. 

Control of the Bath. — The method is illustrated in Ex¬ 
periment 58 (B). After titration, the strength of the bath 
can be restored by suitable additions of hydrogen peroxide, 
or sulphuric acid and sodium peroxide. 

Experiment 58. — Add 5 g. sulphuric acid to 1000 cc. water, 
stir well, and add slowly 4 g. sodium peroxide. Write reaction. 
Don’t leave any sodium peroxide in contact with paper. (Why?) 
Stir the solution thoroughly, and test it with litmus paper. If it is 
alkaline, make it slightly acid with sulphuric acid, and then add 
ammonia until it is faintly alkaline. Save part of the solution 
(Solution 1) for (B). Bleach two 5-gram skeins of wool in 400 
cc. of the solution, boiling very gently for 30 minutes. Save the 
solution (Solution 2) for (B). 

(B) Dissolve 3.2 g. pure dry potassium permanganate in ex¬ 
actly 1000 cc. water. Measure out 25 cc. of Solution 1 with a 
pipette, acidify with dilute sulphuric acid, and dilute to about 
100 cc. with water. 

Titrate the solution with the permanganate from a burette, adding 
it slowly and with constant stirring until a faint pink color appears 
in the solution. The beaker should be put on a white sheet of 
paper. Titrate 25 cc. of Solution 2 in the same way, and calculate 
what part of the hydrogen peroxide has been consumed in 
bleaching. 

Example . — Solution 1 (25 cc.) required 30 cc. permanganate, 
and Solution 2, 5 cc. Then or of the hydrogen peroxide re¬ 
mains after bleaching, and f have been consumed. 


WOOL AND SILK SCOURING AND BLEACHING 129 

Silk. — Raw silk is deficient in brightness, and gener¬ 
ally has a coarse appearance and a harsh feel. It has to 
undergo various treatments, according to the requirements 
of the case. 

(1) Boiling-off\ stripping, or discharging consists in re¬ 
moving all the silk gum which covers the silk and gums the 
individual fibers together. The product is a very brilliant 
silk. 

(2) Half-boiled silk, or sonple silk, has only a portion of 
the silk gum removed. The loss is from 6 to 8 per cent 
instead of 20 to 30 per cent as in the previous operation. 
The silk loses less in weight, but is less brilliant. 

(3) Ecrn silk is raw silk which has been prepared for dye¬ 
ing by removal of the fatty and wax-like impurities. It has 
a harsh feel, is not very bright, but is much stronger than 
boiled-off silk. 

Methods of Boiling off. — Boiling off requires two opera¬ 
tions : — 

(1) Boiling off the Gum. —This operation removes the 
silk gum which covers the thread. It consists in working 
the silk in a soap bath near the boil, containing 25 to 35 
per cent of the weight of the silk of a good, neutral soap. 
The operation requires about an hour, and furnishes the 
boiled-off liquor always used, if possible, as an addition to 
the dye-bath for dyeing silk. Hard water should be puri¬ 
fied. The silk is removed and washed, if necessary, in a 
weak solution of soda. 

(2 ) Scouring. — By this process the last trace of any 
impurity which may remain from the preceding opera¬ 
tion is removed. The silk is inclosed in a coarse bag 


130 


PRINCIPLES OF DYEING 


and boiled for J to 3 hours in a bath containing 10 to 15 
per cent neutral soap. The silk is taken out, washed 
thoroughly, and dried. 

Silk is boiled off as yarn, and in the form of cloth. 

Souple Silk. — The operations are as follows : — 

(1) Scouring. — The silk is worked for about an hour in 
a lukewarm bath containing 3 to 4 per cent soap and J to 
1 per cent crystallized sodium carbonate (soda crystals). 
Fats and oils are removed, and a part of the silk gum. 

(2) Smoothing or Soup ling. — The silk is passed through 
a bath of boiling cream of tartar, about 4 per cent of the 
weight of the silk. It is then washed well. This treat¬ 
ment softens the silk, which otherwise has a harsh feel. 

The tartar bath can be used continuously. If the souple 
silk is to be bleached, after scouring and before smoothing 
it is stovcd , or bleached with sulphur dioxide in the same 
way as wool. It may also be bleached with a dilute solution 
of aqua regia, and then stoved. Souple silk is bleached 
with hydrogen peroxide after it is soupled. 

Ecru silk is simply scoured as in (1) above to remove 
fats and oils. 

Bleaching. — Silk is bleached, like wool, with sulphurous 
acid. Hydrogen peroxide (or sodium peroxide) is also used 
for silk bleaching. The methods are the same as for 
wool. For boiled-off silk, the bath is not heated. 

Other Operations. •— Silk is subjected to other operations 
to increase its length or luster. In stretching , the skeins 
are suspended on a stout wooden peg, and stretched by 
means of repeated jerks on a stout wooden stick placed 
inside the skein. For glossing , the skeins are twisted up 


WOOL AND SILK SCOURING AND BLEACHING 131 

very tight, and allowed to remain so several hours. In 
lustering , the skeins are stretched and steamed at the same 
time. 

Weighting of Silks. — Silk has the power of taking up 
tannic acid and various metallic bodies to a remarkable 
extent, with a corresponding increase in weight, and 
without loss in brilliancy. As silk is expensive, advan¬ 
tage is often taken of this property for the production 
of weighted silks, and silk may be weighted as much as 
200 per cent. The weighting may take place before or 
after dyeing. 

For light-colored silk, the following processes are in 
use: — 

(1) With Tannic Acid. — After dyeing the silk is washed, 
and soaked in a cold solution of tannic acid; it gains 12 to 
15 per cent in weight, and loses somewhat in brightness. 

(2) With Stannic CJdoride (tin spirits). —The raw silk is 
repeatedly soaked in a solution of stannic chloride, and 
washed with water; it may gain in weight up to 25 per 
cent by repeated operations. Repeated soapings at the 
boil are necessary to restore the natural feel to the silk. 

(3) Zinc-phosphate-Silicate Method. —The silk is treated 
with a solution of stannic chloride (pink salts), then with 
sodium phosphate, and finally with sodium silicate. A 
mixture of stannic phosphate and silicic acid is deposited 
on the fiber. By repetitions of the process, silk can be 
weighted up to 150 per cent or higher, without injury to 
its luster or feel. But it loses in strength, and often rots 
without any apparent cause. 

For dark shades or black, silk is weighted: — 


132 


PRINCIPLES OF DYEING 


(1) With impure tannins , as sumac, myrabolans, at an 
elevated temperature. 

(2) With Ferric Tannate. — The silk is worked alternately 
in solutions of tannic acid (in the form of chestnut extract, 
myrabolons, etc.), and pyrolignite of iron, and exposed to 
the air after each treatment to oxidize the ferrous tannate 
first formed. The operations are repeated several times. 
Another method is to impregnate the silk alternately with 
a ferric salt and tannin. Silk is weighted in black dyeing 
up to 200 per cent by this method. The silk must be 
soaped, and brightened with an acid. 

(3) With Basic Ferric Salts. — The silk is impregnated 
with “ nitrate of iron,” and worked in a boiling soap bath 
to fix the ferric hydroxide. The operation is repeated 
seven or eight times if necessary. “ Nitrate of iron ” is a 
basic ferric sulphate, formed by treating copperas (ferrous 
sulphate) with nitric acid. 

Silks heavily weighted are liable to spontaneous com¬ 
bustion. Other methods of weighting are in use. 


CHAPTER XIII 


DYEING MACHINERY AND MANIPULATIONS 

Cotton and wool are dyed in the form of loose cotton or 
wool; as slubbing or sliver; as yarn in skeins and warps ; 
and as cloth. Cotton, in addition, is dyed in the cop. Silk 
is dyed as yarn or cloth. These different forms necessi¬ 
tate the employment of different kinds of machinery and 
different modes of handling. 

Raw Stock. — Loose cotton or wool is dyed for the pro¬ 
duction of colored filling; also to make fancy yarns of dif¬ 
ferent kinds. Loose cotton or wool of different colors is 
sometimes mixed to produce some desired shade. A dark 
color reduced by mixture with white material produces a 
faster shade than one in which all the cotton is uniformly 
dyed. 

The production of even colors is of no great importance 
in dyeing raw stock, as any inequalities are removed by 
the mixing which occurs in the different processes of manu¬ 
facture. The dyer should endeavor to keep the loose ma¬ 
terial as open as possible, as any matting of the fibers 
causes considerable loss in subsequent processes. Dyed 
cotton has a greater wearing action upon the teeth of the 
carding machine than undyed cotton. 

Dyeing. — Raw stock may be dyed in plain vats, being 
stirred with poles. For convenience in handling, it may be 
placed in nets or baskets. 


i33 


134 


PRINCIPLES OF DYEING 


The machine used for dyeing raw stock may be repre¬ 
sented by the Klauder-Weldon dyeing machine (Fig. 9). 
It consists of a drum of heavy copper netting caused to 
revolve in a dye-vat, which is heated by steam-pipes. The 
cylinder is divided into a suitable number of compartments, 
provided with doors. When dyeing, the drum is set in 
motion and caused to revolve in the dye-bath until the 



Fig. 9. — Klauder-Weldon raw stock dyeing machine. 


material is dyed the desired color. This machine can be 
used for boiling off, bleaching, mordanting, and dyeing. 

Washing. — The washing may be performed in the same 
vessels as are used for dyeing, or in the hydro-extractor. 

Drying. — The excess of water is first removed by squeeze 
rolls, or a hydro-extractor (see under Skein Drying). Some¬ 
times cotton is next passed through an opener, so that it 
will come to the drying machine proper in a perfectly loose 
condition. 

There are two types of dryers. In one type the raw 




























DYEING MACHINERY AND MANIPULATIONS 


135 


stock is placed upon shelves of gal¬ 
vanized iron wire netting, in drying 
chambers, which are heated directly, 
or by hot air which is blown through 
by fans. The air may be heated by 
steam, or the chamber may be placed 
over the boilers of the plant. 

In another form of drying machine 
(Fig. 10) the cotton is fed into a hop¬ 
per (A) at one end, on to an endless 
wire apron ( B ), which carries the cot¬ 
ton through successive chambers, 
and delivers it dry at the other end. 
The drying chambers are at a mod¬ 
erately high temperature at the wet 
end, and grade to a lower tempera¬ 
ture at the point of exit. Air is 
blown through the machine by suit¬ 
able fans ( C ). 

Sliver or Stubbing. — The object 
of dyeing carded cotton in the form 
of sliver or slubbing is to produce 
the effects of raw stock dyeing and 
avoid the action of the dyed cotton 
on the cards and the loss due to 
matting of loose cotton during the 
dyeing process. 

Wool slubbing is dyed for the pro¬ 
duction of fancy yarns. 

Sliver or slubbing is placed be- 



Fig. 10.— Raw stock drying machine. (Philadelphia Textile Machinery Co.) 









































































































































136 


PRINCIPLES OF DYEING 


tween two perforated metallic plates or cylinders, and the 
dye liquor is sucked through it by means of a pump. 

Wool slubbing and “ tops ” are also reeled off into skeins, 
and dyed in skein-dyeing machines. 

Skeins. — The object of yarn dyeing is to produce fig¬ 
ured designs by weaving colored threads into the cloth. 
Skeins and cops, as a rule, are used for filling. Skeins are 
dyed more easily than yarn in other forms. Skeins are 
dyed by hand or by machinery. 

Hand Dyeing. — A round tub is employed in some forms 
of hand dyeing, but the ordinary form of dye-vat is rectan¬ 
gular. Vats for dyeing cotton are made smaller than for 
the same quantity of wool. 

Plain vats or tubs are used for dyeing and otherwise 
treating goods cold, or at a lukewarm heat, when a supply 
of hot water is provided. When, however, it is necessary 
to work at or near the boil, the vat must be heated with 
steam. A steam-pipe is placed in the bottom of the vat, 
with a perforated false bottom above it, to prevent the 
material to be dyed from coming in direct contact with it. 
The pipe is usually of copper, sometimes of iron, tin, or 
lead. The pipe usually passes down one corner of the vat, 
which is also boxed off. Dark stains or stripes on goods 
are sometimes due to their coming in direct contact with 
the steam-pipe. If one portion of the bath is hotter than 
other portions, the dyeing may not be uniform. 

The vats are usually heated by direct steam, the pipe 
being perforated so that the steam can pass directly into 
the bath, causing a good circulation of the liquid in it. 
Some of the steam is condensed, and dilutes the dye-bath, 


DYEING MACHINERY AND MANIPULATIONS 137 

but the quantity condensed hardly more than counterbal¬ 
ances the water lost by evaporation and that removed with 
the goods. In some cases, however, it is best to heat the 
bath with a closed steam coil, thus preventing its dilution. 
The water condensing in the coil may be collected and used 
for preparing the dye-baths. 

When direct steam is used, it is essential that the steam 
should be clean and free from particles of oil. Impure 
steam usually results in spots or stains on the dyed goods. 

The skeins are hung upon sticks, usually made of hick¬ 
ory, but ash, beech, or any hard wood that does not swell 
much when treated with water may be used. A pole 
made of a sapling with all the bark removed and the 
branches lopped off is preferred. 

The Operation. — The dye being fully dissolved, a stick¬ 
ful of skeins is placed in the vat, lifted two or three times 
to wet the skeins, and placed in the vat with the ends of 
the sticks resting on its edges. After all the skeins have 
been entered in the same way, the skeins are “turned.” 
The sticks are arranged so as to be about four inches 
apart, and a foot from one end of the vat. Two men lift 
a stick full of yarn, one puts a short stick through all the 
skeins, the one on the other side grasps it and lifts it, thus 
giving the yarn a quarter turn. The stick is placed close 
to the end of the vat, and the others are turned in the 
same way. “ One turn ” has then been given. The dyer 
gives three or more turns, as may be necessary. 

Machine Dyeing. — Various machines have been con¬ 
structed for dyeing skeins. One form is the Klauder- 
Weldon skein-dyeing machine (Fig. 11). 


138 


PRINCIPLES OF DYEING 


On a central axis are built two disks or rod carriers, which 
can revolve in the dye-vat, the revolution being given by 
suitable gearing, which is shown at the side of the ma¬ 
chine. On the outer edge of the disk are clips for carry¬ 
ing rods, on which one end of the skein of yarn is hung, 
while the other end is placed on a similar rod carried near 



the axle. The revolution of the disks carries the yarn 
through the dye liquor, and at a certain point the rods 
carrying the yarn are turned. 

In another form of skein-dyeing machine the yarn is 
hung in a vat on dye sticks, or reels, which are caused to 
revolve by suitable gearing. 

A third machine lifts the skeins, turns them, and puts 
them back in the vat; its action resembling hand dyeing. 

Washing. — Skeins may be washed by hand in dye-vats, 
the operation being the same as dyeing. 

























































DYEING MACHINERY AND MANIPULATIONS 139 

Washing machines for single skeins are constructed 
according to two principles. 

In the first type, the skeins are hung on sticks or rollers, 
which are caused to revolve by suitable gearing, while the 
skein hangs in a vat of water. Fresh water flows in at the 
top and the dirty water flows off at the bottom. 



Fig. 12. — Skein-washing machine. 


In the second type (Fig. 12), the skeins are hung on 
sticks (A) or rollers, which revolve, and at the same time 
move from one end of the vat to the other. The vat in 
the figure is circular so that a single man may handle the 
washed and unwashed skeins. Clean water flows in where 
the washed skeins are taken out ( B ), and the dirty water 





140 


PRINCIPLES OF DYEING 


flows off near where the unwashed skeins are entered (C). 
The skeins thus move in a direction opposite to the flow of 
water — the counter-current system, as it is called. 

Extracting Water. — Excess of water may be removed 
from skeins in three ways: wringing, squeezing, and 
hydro-extracting. 

In wringing, the skein is hung on a hook or short stick 
driven in the wall, and twisted by hand by means of a short 
stick. The skein is turned around, and the operation re¬ 
peated. Wringing machines are used in some branches 
of dyeing. 

In squeezing, the skein is passed between two rollers, 
which are pressed together by means of a spring, or a lever 
and weights. 

The hydro-extractor, or “ whizzer ” (Fig. 13), as it is 
called, consists of a perforated basket of copper, or gal¬ 
vanized iron, arranged in an outer cover so that it can be 
revolved at a high rate of speed. The goods are placed 
in the basket, taking care to distribute them as evenly as 
possible, and the latter set in motion, when the centrifugal 
force throws the water out of the basket into the outer 
casing, whence it flows off. The operation is over in about 
five minutes. Hydro-extractors may be driven by hand 
power, by belts and shafting, by a small steam-engine 
attached directly to them, or by an electric motor. The 
best types of hydro-extractors are provided, as in the figure, 
with arrangements to minimize the unavoidable vibration 
which occurs when they are driven. The machine is hung, 
as a whole, on supports, so that it can vibrate without 
shaking its foundations. 


DYEING MACHINERY AND MANIPULATIONS 


141 

The relative efficiency of wringing, squeezing, and 
hydro-extracting is shown by the following table, which 



Fig. 13. — Hydro-extractor. 


gives the percentage of water removed from the goods 
by the three processes : — 

Wringing cotton yarns . . -45 per cent 

Squeezing . . . . . 72 “ “ 

Hydro-extracting . . . . 82 “ “ 





























































































































































































































































PRINCIPLES OF DYEING 


142 

Drying. — After the excess of water has been removed 
the skeins are dried. They may be placed on sticks, 
which are placed in a drying oven, a room heated by 
steam-pipes or hot air, or a continuous machine similar to 
that for drying loose cotton (Fig. 10) may be used, the 
skeins hung on sticks being placed on an apron at one 
end, and taken off dry at the other end. 

Warps. — Warps to be dyed may be of considerable 
length. Sometimes they are doubled several times, but as 
a rule they are dyed as single warps. The dyeing must 
be so managed that the warp is of uniform color. 

Dyeing Machines. — Warps are always dyed in machines 
which are the same in principle, though they vary in the 
form and arrangement of their parts. Figure 14 repre¬ 
sents one form. The machine consists of a dye-vat (A) 
provided with suitable heating arrangements, and contain¬ 
ing a frame which carries a number of copper rollers ( B ). 
One or more warps may be dyed at a time. The warps 
pass from the boxes, on the overhead frame, between the 
pegs (E), and then pass up and down over the rollers (Z>), 
and finally out between a pair of iron or wooden squeeze 
rollers ( C) into a box set to receive them. The apron ( D ) 
lays the warps evenly in the boxes. The warp has then 
had “ one run.” It is given as many more “ runs ” as may 
be necessary to produce the desired result. For heavy 
warps, the number of rollers is increased. The warps are 
kept separate by guide pegs. 

The machine in the figure is arranged for eight warps. 

Two or more machines are sometimes arranged in series, 
so that the warp passes from one vat into the second. 


DYEING MACHINERY AND MANIPULATIONS 143 

Sizing. — Warps are often sized immediately after dyeing 
in machines constructed on the same principle as the warp- 



FiG. 14. — Warp-dyeing machines. 


dyeing machines. The vats are much smaller, however, 
and only one or two guide rollers are necessary. 

Drying. — The warps are squeezed by the dyeing ma¬ 
chine. They are next dried, usually on iron cylinders 
heated by steam, technically termed “ cans,” or tins (Fig. 
15). The warp passes spirally around the outside of the 












144 


PRINCIPLES OF DYEING 



cans, usually passing over 
from ten to twenty of 
them. The condensed 
water from the cans may 
be collected and used for 
preparing the dye-bath. 
The number of cans used 
varies, and they are ar¬ 
ranged in a number of 
ways, both horizontally 
and vertically. 

Dyeing on the Cop. — 

The object of cop dyeing 
is to avoid reeling yarn 
from bobbins or cops into 
skeins for dyeing, and 
reeling it back again. 
The difficulty in cop dye¬ 
ing is to secure even 
penetration, so that the 
outer and inner layers of 
yarn will possess the 
same color. Only very 
soluble and level-dyeing 
dyestuffs maybe used for 
cop dyeing. 

In the cop-dyeing ma¬ 
chines, the cops are 
placed upon perforated 
metal spindles, which are 


/ 


















































DYEING MACHINERY AND MANIPULATIONS 


145 


so connected with a pump that it sucks the dye liquor 
through the cop and returns it to the vat. The machines 
are made in a variety of forms. 

Cloth. — Cloth when dyed must possess a uniform color, 
free from spots and stripes, and the interior of the fabric 
must be the same color as the exterior. 



Fig. 16. — Dye-beck and wince. 


The dye-beck and wince, the jigger, the padding machine, 
the hawking machine, and the single-color printing machine 
are used for cloth dyeing. They vary somewhat in form 
and size. 

The dye-beck and wince (Fig. 16) consists of a wooden or 
cast-iron vat (A), over which a wince, or skeleton roller 














146 


PRINCIPLES OF DYEING 


( B ), is supported. The vat is divided by a perforated dia¬ 
phragm, which is open below, in order to allow the pieces 
to pass freely beneath it. The pieces, stitched together in 
the form of endless bands, are drawn by the revolution of 
the wince continuously in the same direction, and are pre¬ 
vented from becoming entangled with each other by means 
of a series of wooden guide pegs which divide the several 
pieces. 



Fig. 17. — Jiggers. 


The jig , or jigger (Fig. 17), consists of a dye-vat (A) 
larger at the top than at the bottom, containing three guide 
rollers. The cloth is wound on a roller ( B ), passed over 
the guide rollers in the vat, on to a second roller (C). 
When the machine is set in motion, the cloth is wound 
from the first to the second roller. The direction is then 
reversed, and the cloth wound back again, and so on as 
long as may be necessary. When the dyeing is finished, 





























DYEING MACHINERY AND MANIPULATIONS 


147 



the cloth is wound on a third roller ( D ) called the batch 
roller , and the operation is called batching. For some kinds 
of dyeing, the jigger is provided with a pair of squeeze 
rollers to squeeze out the excess of dye liquor before 
batching. 


FlG. 18. — Padding machine. 

The padding machine (Fig. 18) is used chiefly for dyeing 
light colors on cotton cloth. The cloth passes through the 
thickened dye liquor contained in the vat (A), then between 
squeeze rollers (B), and on to a second roller (C). The 
operation is then finished. The operation really consists 





148 


PRINCIPLES OF DYEING 


in impregnating the cloth with a colored solution and dry¬ 
ing it. The depth of color depends upon the strength of 
the solution, and the pressure of the squeeze rollers. 

The single-color printing machine (Fig. 19) is used for 
padding cloth on one side only ( slop padding ). The piece 

passes around a large iron roller 

(A) , which presses against the 
copper or brass printing roller 

( B ) . The latter is fed with 
color by a wooden roller ( C ) 
which runs in the thickened 
color or mordant in the color- 
box ( D ). The surface of the 
printing roller is engraved with 
fine lines which take up more 
or less color according to the 
depth of the engraving. The 
excess of color is scraped off 
the printing roller by a steel 
blade (E), the color doctor. 

fig. 19.— Single-color printing Between the cloth and the iron 

roller is a thick band of felt, 
called the blanket , and a second band usually runs between 
the blanket and the cloth, to prevent the blanket from 
being soiled. 

The hawking machine is used in the case of dyes which 
must not be exposed to the air. It consists of a series 
of guide rollers arranged in a vat so as to be covered by 
the dye liquor. The cloth is sewed together in the form 
of an endless belt, and drawn continuously in an open 
form through the dye liquor by means of a pair of rollers, 





DYEING MACHINERY AND MANIPULATIONS 149 

driven by suitable gearing, and placed beneath the surface 
of the liquid. 

In dyeing with the dye-beck and wince, the quantity of 
water used must be relatively large in proportion to the 
amount of goods. A smaller quantity of water and 
stronger solutions of dye may be used with the jigger. 

Drying. — The cloth is squeezed, opened, if necessary, to 
its full width, and then dried on cans similar to those used 
for warps. It may also be dried by passing up and down 
through a hot chamber, emerging dry at the other end. 

Printing of Stubbing and Warps. — Slubbing is printed 
in stripes for the production of certain kinds of yarns, and 
printed warps are necessary for the production of some 
classes of figured goods. 

The machine used is similar to the single-color printing 
machine (Fig. 19); as many printing rollers are used as 
may be necessary. Usually the printing roller is fluted, 
but any design desired may be engraved upon it. The 
color remains in the engraved parts of the roller, being 
scraped from the other parts by the color doctor. The 
engraving must be much deeper for slubbing than for 
warps, and the blanket should be softer. 

Warps are printed after they are beamed. 


CHAPTER XIV 


GENERAL OBSERVATIONS ON DYEING 

Material which has been properly dyed is of a uniform 
color in every part, free from spots or streaks of every 
kind, and with the interior of the fabric the same color as 
its exterior. For the production of level dyeing, as it is 
called, every dye and class of dye has its special character¬ 
istics and methods of application, which vary with the 
kind of fiber and the nature of the material. But there 
are certain considerations which are applicable to every 
class of dyes, and every kind of dyeing, and it is these 
which will here be presented. 

Dissolving the Dye.—It is essential that the dyestuff 
should be uniformly distributed through the dye-bath. In 
the case of insoluble colors, which occur in the form of 
pastes, the dyestuff is mixed with water, and poured into 
the bath through a strainer of cloth. Soluble colors, which 
occur as powders or pastes, must, as a rule, be dissolved 
very carefully, as undissolved particles will often produce 
dark spots on the goods, known as dye-spots. Boiling 
water may be used for most dyestuffs, with the exception 
of certain colors which are decomposed by boiling water 
and can be dissolved in warm water only. Some few 
colors require solution in alcohol. The solutions should 
be poured into the bath through a filter, to catch undis¬ 
solved particles. 

150 


GENERAL OBSERVATIONS ON DYEING I 5 I 

Hard Water. — Hard water is generally injurious in 
dyeing, as in most cases it precipitates a portion of the 
dyestuff, either in the form of a calcium salt, or, in the 
case of basic dyes, as the color base. If pure water is not 
available, hard water should usually be softened before 
the dye is added to the dye-bath. 

The methods for softening water on a small scale are as 
follows: — 

(1) The water is boiled. This removes temporary hard¬ 
ness only, calcium carbonate being precipitated according 
to the following reaction : — 

Ca(HC 0 3 ) 2 = CaC 0 3 + H 2 0 + C 0 2 . 

(2) The water is boiled with the addition of sodium 
carbonate. Both temporary and permanent hardness are 
removed by this method, calcium sulphate being decom¬ 
posed as follows: — 

CaS 0 4 + Na 2 C 0 3 = Na 2 S 0 4 + CaC 0 3 . 

(3) The water is boiled with the addition of soap. 
Insoluble calcium salts of the fatty acids of the soap are 
formed, and appear as a scum on the surface of the water. 

In each of the three cases, the boiling should continue 
for five or ten minutes. The water may be allowed to 
settle, and be drawn off from the sediment, but this is not 
always necessary. The amount of softening agents to be 
used depends upon the hardness of the water. 

(4) The water is neutralized or corrected with acetic acid 
(applicable for basic dyes only). The hardness is really 
not removed, but as the water is no longer alkaline, it will 
not precipitate basic dyes. 


152 


PRINCIPLES OF DYEING 


Correction of Water. — A liter of the water to be cor¬ 
rected is poured into a porcelain basin, tinted with methyl 

orange, and titrated with — hydrochloric acid (io cc. 

hydrochloric acid 34.2 Tw. per liter of water). The acid 
is delivered from a burette until the color of the liquid 
just changes. 

The number of cubic centimeters of acid required multi¬ 
plied by 0.26 gives the number of ounces of acetic acid 
of 9 0 Tw. required to neutralize or correct 100 gal. of 
water. 

Other impurities in water cause trouble. Water which 
contains appreciable amounts of iron cannot be used in 
dyeing or bleaching without purification. Organic matter 
in water sometimes reduces a dye, thus leading to defective 
colors. 

Water Purification. —As hard water consumes soap and 
dye and causes trouble with boilers in many plants, it is 
economical to install a plant for the purification of water, 
to be used for boilers, for dyeing, and for wool washing. 
A thousand gallons of water of 1 degree of hardness will 
destroy i |- lb. soap, so if the water used in wool scouring 
has over 5 to 10 degrees of hardness, the loss of soap will 
be considerable. The softening is usually accomplished 
by means of a mixture of sodium hydroxide and calcium 
hydroxide (slaked lime), which precipitates the calcium 
salts as calcium carbonate. The apparatus in use varies. 
It may consist of an upright tank with a number of inclined 
partitions on which the calcium carbonate may settle as the 
water rises slowly to the top of the vessel; or the calcium 
carbonate may be filtered out in a filter press. 


GENERAL OBSERVATIONS ON DYEING 


153 


Waste water from large dyeing or bleaching establish¬ 
ments should usually be purified before it is allowed to flow 
off. The methods to be followed depend upon the nature 
of the impurities. 

All the water can be run into a large tank, where many 
of the impurities precipitate each other; the precipitation 
may be completed by the addition of slaked lime mixed to 
a paste with water ( milk of lime). The water is then 
allowed to settle, or is filtered, and run off. 

Production of Level Dyeings. — In all apparatus used 
for dyeing, some portions of the material are always less 
exposed to the action of the dye liquor than other portions, 
being out of the bath, or protected by folds of cloth, etc. 
In general, the dye must not be taken up too rapidly by 
the fiber, or portions of the material will get more than 
their share. In the jigger, for example, if the absorption 
takes place too rapidly the first portions of the cloth to 
pass through will take up the greater part of the dye. 

The general methods for retarding the absorption of a 
dye are as follows: — 

(1) Regulating the Temperature. — As a rule, the absorp¬ 
tion of dyestuffs increases with the temperature of the 
dye-bath. By entering the goods at a low temperature, 
and raising the temperature slowly, level dyeing is pro¬ 
moted. 

(2) Regulating the Addition of Dyestuff. — Instead of 
making the addition of all the dye at once, it is added in 
portions to the bath. This method is of advantage in 
warp dyeing, and in dyeing on the jigger. 

(3) The Proper Use of Assistants. — Some assistants 


i 54 


PRINCIPLES OF DYEING 


cause the dye to go on the fiber more rapidly, while others 
decrease the rate of its combination with the fiber. By 
the addition of the assistants at earlier or later stages 
of the operation, or by increasing or decreasing their 
amount, the rate of absorption of the dyestuff may be 
largely controlled. 

Special methods required by each class of dyestuffs are 
given in their proper place. 

The rate at which the absorption of dye may safely be 
allowed to take place depends upon four things : the thick¬ 
ness of the material to be dyed, the depth of color to be 
produced, the kind of machine which must be used, and 
the nature of the fiber itself. 

Thickness of the Material. —Thick cloth, heavy warps, 
and tightly spun yarn are less easily penetrated by so¬ 
lutions, and must be dyed at a slower rate than thinner 
material or soft yarns, which are easily penetrated. Too 
rapid absorption of the dye leads to deficient penetration, 
i.e. the interior of the cloth or warps will be a lighter color 
than the outer portions, or the dye may be fixed super¬ 
ficially, and not be fast to rubbing. 

Depth of Color. — Dark shades may be dyed more rapidly 
than light colors, as the large quantity of color present 
affords all portions a more equal chance to become dyed. 
Light colors must always be dyed much more slowly and 
cautiously. 

Kind of Machine. — Raw stock does not require level 
dyeings, as inequalities are removed in subsequent processes 
of carding and spinning. 

Cop dyeing calls for very level dyeing colors, and great 
precautions in delaying the absorption of the color, to 


GENERAL OBSERVATIONS ON DYEING 


155 


insure an even shade in all parts of the yarn, as yarn on 
the cop is penetrated slowly by the liquor. 

Skeins are comparatively easily dyed. 

For the warp-dyeing machine, and the jigger, the color 
solution must, as a rule, be added in several different 
portions during the passage of the warp or cloth. 

The Fiber. — Cotton has slight affinity for dyes, and in 
dyeing it with direct colors it requires few precautions for 
retarding the absorption of the dye. When a mordant 
is used, the combination takes place between dye and 
mordant, and the precautions to be used depend on their 
nature rather than that of the fiber. Wool and silk have 
such affinity for dyes that it is necessary to prevent them 
from being absorbed too rapidly. 

Feeding of Colors. — When goods are allowed to remain 
in the dye-bath while it cools down, a further absorption of 
dye called “ feeding ” takes place, which is often of ad¬ 
vantage, but sometimes is a disadvantage. If the material 
is piled up, or hung on poles while still wet from the dye- 
bath, and left too long, the dye liquor will descend to the 
lowest parts of the mass, and by feeding produce uneven 
shades. Similar faults result in dyeing with the jigger 
when the cloth, saturated with the dye liquor, is allowed to 
remain too long on the batch roller before squeezing or 
washing. 

Standing Baths. — In many processes of dyeing, the dye 
or reagents are only partly removed from the bath. It is 
often an advantage when several lots are to be dyed the 
same color to use the same bath over and over again, 
restoring its strength each time after using by suitable 


156 


PRINCIPLES OF DYEING 


additions. The use of standing baths, as they are called, 
saves time in making up a new bath, saves the dye or salts 
in the old bath, and often saves the time or heat required 
to raise the temperature of the new bath. Of course, in 
time the standing baths become dirty and must be thrown 
away. 

Mixing of Dyes. — Comparatively few dyeings are made 
with single dyestuffs. 

Dyes are combined in two ways: by mixtures in the 
same bath and by topping a color with other dyes. For 
mixing in one bath, dyes of the same class must be used; 
the methods of topping depend somewhat on the nature of 
the colors, though basic colors are usually used for top¬ 
ping. The principles of color mixing are given in another 
chapter. 

Dyeing to Shade. — Dyers are usually called on to match 
a certain color. Matching a given color is called dyeing 
to shade. In dyeing to shade, it is better to start with too 
little dyestuff in the bath than too much, as a deficiency is 
easily corrected. When the dyeing operation is nearly 
finished, the dyer removes a sample of the goods (which 
may be small pieces of the goods attached to it for that 
purpose), dries the sample, which alters its color, and com¬ 
pares it carefully with the color to be matched. This is 
done in two ways: the dyer first holds the two samples 
side by side between him and the light, and catches the 
reflection from the material, and then he turns and ex¬ 
amines it with his back to the light. If the color is cor¬ 
rect, but too light, more of the dyestuff is added, and the 
operation continued. If the color does not have the correct 


GENERAL OBSERVATIONS ON DYEING 157 

hue, other dyestuffs are added to the bath; or the color 
may be topped in another bath. Small additions to a dye- 
bath should always consist of easily leveling colors. 

In color matching, the nature of the light is of consid¬ 
erable influence. The best lights are: the light from a 
northern exposure, an electric arc light, or burning magne¬ 
sium ribbon. Ordinary gas-light and lamplight are too 
red to give the correct tone to color. 

When the eye has been tired by matching a number of 
colors of the same shade, it may be rested by looking at 
the complementary color to those matched. 

In matching a color, the dyer must consider the effect 
of the subsequent operations which the material is to go 
through. Sizing may affect the color, and cloth is fre¬ 
quently heated or ironed in finishing, which has the effect 
of changing the shade of a number of coloring matters. 
For example, some blues have a tendency to become redder, 
and some yellows are liable to incline toward orange. 

Fastness of Dyes. — The methods for estimating the fast¬ 
ness of colors to perspiration (Exp. 9), alkalies (Exp. 10), 
washing (Exp. 7), boiling water (Exp. 6), rubbing (Exp. 36), 
and milling (Chapter IX) have already been given. Of 
course, the best test for any color is practical trial of it. 

Fastness to Cross-dyeing. — Dyed cotton which is to be 
woven with woolen yarn when the latter is to be dyed in 
an acid bath (as with Biebrich scarlet) must be fast to cross¬ 
dyeing. 

Test: — Plait the yarn with wool and boil for 20 minutes 
in water containing 1 gram sulphuric acid per liter, rinse 
and dry. The extent of bleeding should be noticed. 


i 5 8 


PRINCIPLES OF DYEING 


Fastness to Bleaching. —Colored threads are sometimes 
woven in cotton goods afterward to be bleached — for 
example, the headings of towels. The color must be fast 
to bleaching. Comparatively few dyes stand this test. 

Test: — Treat the dyeing for 15 minutes in a solution of 
bleaching powder at |° Tw., sour with dilute hydrochloric 
acid and wash. 

<1 

Fastness to Stoving. —The color must resist the action 
of sulphur dioxide. Colored yarns to be woven with wool 
which is to be bleached with sulphur must stand this test. 

Test: — Moisten the dyed material, and place it in a 
closed vessel with a piece of burning sulphur, for 12 hours. 

Fastness to Ironing and Calendering. — Many coloring 
matters are altered on ironing or drying, though the change 
in almost all cases is temporary. It may prove trouble¬ 
some in color matching. 

Test: — Press the material with a hot iron, and note any 
change in shade. 

Fastness to Carbonizing. — Test: — Saturate the dyeing 
with a 5 per cent solution of sulphuric acid, wring out and 
dry between undyed woolen material at about 92 0 C., then 
pass through a 1 per cent solution of sodium carbonate, 
rinse and dry. 

Fastness to Potting. — Dyes which are fast to potting 
must stand steaming under pressure. 

Fastness to Light. — The fastness of a dye to light varies 
with the material on which the dyeing is made, and on the 
depth of the dyeing, light colors being affected very much 
more rapidly than dark ones. The intensity of light varies 
with the season of the year and the latitude and weather 
of the place. The fastness of a color to light is to be 


GENERAL OBSERVATIONS ON DYEING 


159 


determined by comparing the sample to be tested with 
other samples of known fastness exposed at the same time. 

Test: — Expose the sample to be tested, dyed a moder¬ 
ately dark shade, to direct sunlight under glass, protected 
from rain but with free access of air. The exposure should 
be made facing the south if possible. A sample of the 
material is preserved in a dark box, for comparison. 
Expose, at the same time with the sample to be tested, 
three samples of wool dyed with ( a ) quinoline yellow S or 
indigo carmine (fugitive colors); (b) congo orange R or 
alkali blue 6B (moderately fast); and (e) chrysamine G 
or naphthol blue black (fast colors). The samples should 
be examined every month, and the exposure stopped when 
one-half of the color to be tested has been destroyed. If 
this occurs before the color of quinoline yellow S or indigo 
carmine has been affected, the color is very fugitive; if 
approximately one-half of the quinoline yellow S has been 
destroyed, the color is fugitive. If, when one-half of the 
color to be tested is destroyed, one-half of the color of 
Congo orange R or alkali blue 6 B has disappeared, the 
color is moderately fast; if one-half of chrysamine G or 
naphthol blue black, it is fast. Finally, if when one-half 
of chrysamine G or naphthol blue black is destroyed, the 
color is hardly affected, it may be considered as very fast 
to light. 

The terms applied to the fastness of colors to light are 
defined as follows : — 

Very Fugitive. — The colors fade almost completely 
after exposure for 3 weeks to the sun in summer. 

Examples. — Naphthol yellow S, new methylene blue N, 
and methylene green. 


160 PRINCIPLES OF DYEING 

Fugitive. — They fade markedly in 6 weeks, and entirely 
at the end of a year. 

Moderately Fast. — They fade distinctly in 6 weeks, and 
almost completely in a year. 

Fast Colors. — They fade little in 9 weeks. 

Very Fast. — After a year’s exposure, a moderately good 
color remains. 

Examples. — Alizarin cyanin R, and curcumin S. 

Requirements for Fastness. —The fastness required of 
different goods varies according to the use to which they 
are to be put. The following are given as examples : — 

Loose wool, slubbing, and weaving yarns must be dyed 
fast to light, milling, and potting. 

Sewing cotton, carpet yarns, velvet, and plush must be 
dyed fast to light and rubbing. 

Hosiery yarns require fastness to washing, perspiration, 
and rubbing. 

Yarns for flannels, rugs, and blankets require a moder¬ 
ate fastness to milling, good fastness to perspiration and 
rubbing. 

Cotton linings must be dyed fast to perspiration, rub¬ 
bing, and calendering. 

Shirt goods must be fast to light, rubbing washing, and 
perspiration. 

Gentlemen’s suitings must be fast to light and potting. 
The color must not rub off, and the goods must be well 
dyed through. The colors of military cloth should be 
particularly fast to light. 

Ladies’ dress goods must be fast to light, rubbing, and 
alkaline street dust. 


GENERAL OBSERVATIONS ON DYEING l6l 

Defects in Dyeing. — The defects in dyeing to which 
each class of colors is liable are given under the descrip¬ 
tion of that class. We will here consider only some causes 
of defects not peculiar to any class of dye. 

In cotton dyeing, unripe cotton fibers cause white specks ; 
motes and oil spots lead to defects. Other defects may be 
traced to faults in bleaching. 

In wool dyeing, hemps lead to defects in dyeing. Irregu¬ 
lar dyeing may be caused by injudicious blending of dif¬ 
ferent qualities of wool, which have different degrees of 
affinity for the dye; by irregular weaving; by the use 
of yarns not uniform in size, or twisted in different direc¬ 
tions, or twisted with different tensions. Imperfect scour¬ 
ing of raw wool, by which wool grease is left on the fiber, 
will lead to defective dyeing. After scouring, wool should 
be thoroughly washed, as the presence of alkaline bodies 
(soap or sodium carbonate) may cause trouble. Lime in 
pulled wool must be removed before dyeing; the wool 
is treated with hydrochloric acid, washed thoroughly, 
and scoured. Dark spots may be caused by the sulphur in 
wool; if it comes in contact with iron, copper, tin, or lead 
while in the alkaline condition, as in scouring, the sul¬ 
phides of these metals may be formed, and produce dark 
spots. 

Bleeding or rubbing is sometimes due to insufficient 
washing of the cotton or wool after mordanting, or after 
dyeing; in the case of wool, especially when dyeing with 
direct cotton colors and mordant colors, these defects may 
also be caused by not boiling the wool with the dye for a 
sufficiently long time. On the other hand, overboiling 
may injure some colors, such as logwood, which are 


M 


i 62 


PRINCIPLES OF DYEING 


applied on a potassium bichromate mordant, on account of 
over-oxidation of the color. Carbonized wool, which has 
been insufficiently washed, is liable to be dyed unevenly. 

The presence of certain metals must be avoided in 
particular mordant or dye baths. Copper affects the shade 
of some dyes injuriously, and so does iron, and their 
presence must be avoided in such cases. The effect of 
iron in a dye or mordant bath may be counteracted by 
placing a block of zinc in the bath; with this precaution, 
even iron vessels may be used. 

Soaping. — Dyeing with certain colors, especially on cot¬ 
ton, is followed by working in a warm soap bath, or 
soaping. Soaping has the following objects: — 

(1) It gives the material a softer feeling, and brightens 
the color. 

(2) It removes loosely adhering particles of dye, and so 
prevents rubbing. 

(3) It neutralizes any traces of mineral acid, and pre¬ 
vents tendering of cotton (a fatty acid is formed, which 
does not injure the fabric). 

A careful soaping, after the production of some colors, 
is absolutely essential if freedom from rubbing is desired. 

Silk Dyeing. — Silk dyeing is always carried out with 
the addition to the dye-bath of soap, or preferably boiled- 
off liquor, the alkaline liquor which results from the scour¬ 
ing and boiling off of raw silk with soap. 

The boiled-off liquor acts in two ways: it preserves the 
luster and peculiar crisp feel of silk (known as the scroop 
feel), and it retards the combination of dyestuff with the 
silk fiber, thus aiding in the production of level shades. 


GENERAL OBSERVATIONS ON DYEING 163 

The silk gum in solution combines with the dyestuff, first, 
and afterward the dyestuff is taken up more slowly by 
the fiber. The amount of boiled-off liquor to be employed 
depends upon the nature of the coloring matter employed; 
as a rule, it is about one-fourth to one-third of the total 
volume of the dye liquor. In silk dyeing, the dye-bath is 
seldom heated to a boil. 

After the dyeing operation, silk is always “brightened,” 
which gives it the scroop feel. It is passed through water 
slightly acidified with acetic, sulphuric, or tartaric acid, and 
rinsed without washing. The choice of acid depends to 
some extent upon the nature of the dyes employed. 


CHAPTER XV 


DIRECT COTTON COLORS 

The direct cotton colors are salts of color acids, and are 
direct dyes for all fibers. Since the first member of the 
group, Congo, was discovered in 1884, great numbers of 
direct cotton colors have been placed on the market. The 
number is daily increasing. 

Properties. — All the direct cotton colors are soluble in 
water, with the exception of some sulphur colors, which 
are soluble in sodium sulphide. They vary somewhat in 
solubility. 

Like Congo, they are decomposed by acids, the color acid 
being set free, as represented by the equation below : — 

NaAc + HC 1 = NaCl + H Ac, 

in which HAc represents the color acid. If the acid is a 
different color from the salt, the dye is not fast to acids. 
(How does acetic acid affect congo ?) 

Hard water precipitates most of the direct cotton colors 
in the form of calcium or magnesium salts. It should be 
softened before use in a dye-bath (see Exp. 5). 

Some of the direct cotton colors also form insoluble salts 
with copper or chromium, which are less easily affected by 
light or washing than the corresponding sodium salts. Use 
is made of this property in the after-treatment of certain 
dyes, to increase their fastness. In other cases, the pres- 

164 


DIRECT COTTON COLORS 165 

ence of copper in the dye-vat must be avoided, on account 
of its effect on the color. 

Some direct cotton colors (such as primuline) can be 
diazotized and developed with the production of a color 

possessing a high degree of fastness to washing. 

% 

Application to Cotton. — The direct cotton colors are ex¬ 
tensively used for dyeing cotton. On loose cotton, they 
have the advantage of leaving the cotton soft and in good 
condition for spinning. On yarn in cops, they are used on 
account of their easily leveling properties. On other classes 
of materials, the simplicity of the methods for applying 
them is a great advantage. 

Methods of Dyeing. —The four chief methods of dyeing, 
differing, however, only in regard to the assistants added to 
the dye-bath, are as follows : — 

(1) Dyeing with Glauber s Salt or Common Salt and 
Soda. — This may be regarded as the usual method, 
being employed with the majority of the dyestuffs, and 
for almost all shades. If it is necessary to retard the ab¬ 
sorption of the dye, — as may be the case of pale tints, or 
thick materials which are difficult to dye through, — it is 
best to dye first for half an hour with soda, then add the 
Glauber’s salt. 

(2) Dyeing with Glaubers Salt or Sodium Chloride 
Alone. —This is used for dyes which cannot be dyed in 
the presence of soda; also for dyestuffs which are slowly 
removed from the dye-bath. 

(3) Dyeing with Glauber s Salt or Common Salt and 
S oa p. —This method is to be employed in all cases where 
slow dyeing is necessary, especially in the production of 


PRINCIPLES OF DYEING 


166 

delicate tints, or compound shades which are not easily 
matched, or with materials which cannot be properly dyed 
through by any other means. 

(4) Dyeing with Salts and Caustic Soda. —The dyestuff 
is dissolved in caustic soda, and the solution added to the 
bath. Some dyes of this class require an after-treatment 
with sulphuric acid. 

Other methods are used in particular cases. 

The quantity of assistants to be used depends upon the 
nature of the dye and the depth of the color, — for light 
colors, one-half, and for delicate tints even one-fourth, of 
the quantity used for medium and dark shades. 

The general method of dyeing is as follows : — 

If soap, soda, or sodium phosphate is used, hard water 
may be softened by boiling it after the addition of any 
of these assistants. The bath is then prepared with the 
requisite ingredients, the. color solution is added at once, 
and the material is entered at or near the boiling-point, and 
dyed at these temperatures 30 to 60 minutes. The goods 
may be dried without washing. In the case of goods sen¬ 
sitive to acids, their fastness is increased by a passage 
through a 5 per cent solution of sodium carbonate before 
drying. 

Cold Dyeing. — Some of the direct cotton colors may be 
applied in a cold dye-bath. 

Experiment 58. — Prepare a dye-bath with 2 percent benzo- 
purpurin 4 B and 20 per cent sodium chloride in 200 cc. water ; 
enter a 10-gram skein of cotton yarn, heat to boiling, and boil half 
an hour, or until the skein is uniformly colored. Wash after dyeing. 

Dye as above with 2 per cent diamine scarlet B, 50 per cent 
Glauber’s salt, and 10 per cent soap. 


DIRECT COTTON COLORS 


167 


Dye with 2 per cent chrysamine G and 20 per cent salt. 

Dye with 2 per cent chrysophenin G and 20 per cent salt. 

Dye with 2 per cent diamine blue 3 B, 20 per cent salt, and 
3 per cent soda. 

Dye with 2 per cent Chicago blue 4 R and 20 per cent salt. 

Dye with 2 per cent congo orange R and 10 per cent salt. 

Dye with 2 per cent toluylene orange G and 10 per cent Glau¬ 
ber’s salt. 

Dye with 2 per cent catechu brown and 10 per cent salt. 

Dye with 2 per cent chromanil brown G and 10 per cent salt. 

Dye with 2 per cent diamine violet N, 20 per cent Glauber’s 
salt, and 3 per cent sodium carbonate. 

Dye with 3 per cent oxamine violet and 5 per cent salt. 

Dye with 2 per cent brilliant benzo green and 10 per cent salt. 

Dye with 5 per cent pluto black G and 10 per cent salt. 

Dye with 5 per cent diamine black BH and 10 per cent salt. 

Dye with 5 per cent diamine black HW and 10 per cent salt. 

What is the difference between the three blacks ? Test fast¬ 
ness of all dyeings to acids, alkalies, and washing. 

Assistants. — The dyeing of cotton with direct cotton 
colors always takes place in the presence of assistants, 
which are the neutral salts, Glauber’s salt (sodium sulphate) 
and common salt (sodium chloride), and the alkaline sub¬ 
stances, soap, soda, and sodium phosphate. The presence 
of alkaline substances (sodium carbonate, soap) retards the 
absorption of the coloring matter by the fiber, whereas the 
neutral salts (Glauber’s salt, common salt) have the opposite 
effect; and the more salt the bath contains, the quicker the 
absorption takes place. Of course, undue excess of salt 
tends to precipitate the coloring matters, or to give irregu¬ 
lar shades. 

If added in considerable quantities, the salts raise the 
boiling-point of the dye-bath ; and the increase in tempera- 


PRINCIPLES OF DYEING 


168 

ture thus obtained, though small, is of importance with 
some dyestuffs. 

Glauber s salt is prepared by the action of sulphuric acid 
upon common salt. It occurs in two forms, — as crystals 
containing 55.9 per cent water, of the formula Na 2 S 0 4 -f- 
10 H 2 0 , and as the desiccated or anhydrous salt. 100 parts 
of desiccated Glauber salt are equivalent to 220 of the crys¬ 
tallized salt. Glauber’s salt is sometimes adulterated with 
common salt. 

Common salt , or sodium chloride NaCl, is found as rock- 
salt and in sea-water. It contains no water of crystalliza¬ 
tion. Common salt and Glauber’s salt have the same action 
in dyeing with direct cotton colors, though Glauber’s salt 
often gives the better results. 

Sodium phosphate , or phosphate of soda, is found as 
crystals of the formula Na 2 HP 0 4 -f 12 H 2 0 . Its high 
price prevents it from being used in dyeing to any 
extent. 

Sodium carbonate occurs as crystals, Na 2 C 0 3 + 10 H 2 0 , 
containing 62.9 per cent water, known as soda crystals; 
as crystals carbonate, Na 2 C 0 3 + H 2 0 , containing 18 per 
cent water; and as water-free sodium carbonate, known 
as soda or “soda ash.’’ Soda ash comes into the market 
in various strengths, chiefly 48°, 52 0 to 56°, and 58°, each 
degree indicating 1 per cent sodium oxide (Na 2 0 ). Soda 
ash 58° contains over 58 per cent Na 2 0 , or from 98 to 99 
per cent sodium carbonate, and is pure enough for all dye¬ 
ing operations. The other brands contain chiefly harmless 
impurities, as sodium sulphate and sodium chloride; also 
some caustic soda, which is objectionable for some applica¬ 
tions, while it is an advantage for others. 


DIRECT COTTON COLORS 


169 


Production of Level Colors. — Direct cotton colors pro¬ 
duce level dyeings on cotton with no particular precautions. 
The general rules for the production of a level color 
(Chapter XIV) apply here. 

Cop Dyeing. —The dyeing is conducted at about 6o° C., 
and the Glauber's salt is added after working five or ten 
minutes. In producing compound shades, it is best to dis¬ 
solve each color separately, add about § to the dye-bath, and 
the remainder gradually until the desired shade is produced. 

Warps. — It is best to dissolve dyes and assistants 
separately, add ^ to the dye-bath, and the remainder dur¬ 
ing the passage of the warp. 

Cloth. — On the jigger and the padding machine, the 
same method may be pursued as for warps. 

Mixing Direct Cotton Colors. — The direct cotton colors 
may be mixed unreservedly with each other in the same 
bath, so that almost any shade can be obtained by employ¬ 
ing them in suitable combinations. In selecting dyes to be 
mixed, care must be taken to choose those which behave 
similarly both as regards absorption by the fiber and 
exhaustion of the bath. So far as is possible, it is best 
to select dyestuffs which require the same salts, alkalies, 
etc., in the bath. If this cannot be done, the addition of 
assistants is regulated by the dyestuff present in largest 
proportion. 

Exhaustion of the Bath. — Cotton rarely removes direct 
cotton colors completely from the bath. The quantity left 
in the bath depends on : — 

(1) Volume of water used being greater as the quantity 
of water increases. 


PRINCIPLES OF DYEING 


170 

(2) The quantity of salts used being less with increase in 
quantity of neutral salts. 

(3) The Affinity of Dye for Fiber. — In this respect there 
is great variation. Some few of the group exhaust com¬ 
pletely even when dyeing deep shades. 

Except in the production of very light shades, which 
must be dyed slowly, and for which the exhaustion of the 
bath is of no consequence, the quantity of water in the 
bath should be reduced as much as possible. As a general 
rule, from 20 to 25 gal. of water should be used per 
10 lb. goods to be dyed. Strong baths not only exhaust 
better, but produce deeper and fuller shades. 

The exhaustion of the bath may be facilitated : — 

(1) By working with a closed steam coil (the bath is not 
diluted with condensed steam). 

(2) By increasing the quantity of salts used. 

(3) By allowing the goods to cool in the bath for half 
an hour or longer, when “ feeding ” occurs. 

Standing Baths.—When light shades are dyed with the 
direct cotton colors, the bath is often thrown away. With 
dark shades, however, one-third to one-fourth of the dye 
remains in the bath, as well as a large quantity of salts, 
and it is economical to use the same bath over and over 
again. Standing baths require the addition of water, to 
replace the loss by evaporation, or that carried away in the 
goods, salts, and dye to replace that taken off in the dyed 
material. 

The quantity of salts in the bath may be controlled by 
the use of a delicate hydrometer. The density of the dye- 
bath is determined before and after dyeing, care being 


DIRECT COTTON COLORS 


I/I 

taken that both determinations are made at the same 
temperature. Sufficient salts are then added to bring the 
bath to its former density. 

In dyeing with a mixture of such colors as are not 
equally absorbed by the fiber, a little more of one than 
of the other is left in the bath. For a standing bath, a 
method of estimating and utilizing the color is to enter the 
next lot of goods without further addition of dyes. After 
allowing the residual color to be fully absorbed by the 
material, the shade thus obtained is examined, and from 
its appearance the practised eye can tell in what propor¬ 
tions the several colors should now be added in order to 
match the required shade. 

After-treatment of Direct Cotton Colors. — Three methods 
of after-treatment for the purpose of increasing the fast¬ 
ness of direct cotton colors to light or washing are in use : — 

(1) Diazotizing and developing. 

(2) Coupling. 

(3) Treatment with metallic salts. 

Diazotizing and Developing. — The process consists of 
three steps: dyeing, diazotizing, and developing. For the 
chemistry of this process see p. 16. The dyeing is con¬ 
ducted in the usual way. After rinsing, diazotizing takes 
place in a bath made up with sulphuric or hydrochloric 
acid and sodium nitrite. The following precautions are 
usually necessary in diazotizing : — 

(1) The bath should be kept cold, with ice if necessary. 

(2) Development should take place as soon as possible 
after diazotizing, and the diazotized material should not be 
exposed to direct sunlight, or kept in a warm place. 


172 


PRINCIPLES OF DYEING 


The diazotizing bath is used continuously, being fresh¬ 
ened up with about J the quantity used for the first bath. 

Control of the Diazotizing Bath. — The strength of the 
diazotizing bath may be exactly controlled by the following 
method: — 

Dissolve 3.3 g. potassium permanganate in a liter of 
water. Measure off 25 cc. of the diazotizing bath with a 
pipette, dilute to 200 cc., add a few drops of sulphuric 
acid, and then, from a burette, permanganate solution until 
the liquid assumes a faint pink color. After diazotizing, 
this operation is repeated, and sufficient nitrite and acid is 
added to the bath to bring it to its former strength. For 
example, if 45 cc. of permanganate solution is required 
before, and 30 after, diazotizing, the addition of ^ the 
quantity of nitrite and acid first used will restore the bath 
to its former strength. 

Developing. — After diazotizing, the goods are entered 
into a bath of the proper developer, worked about 15 min¬ 
utes, rinsed, soaped if necessary, and dried. 

The various developing baths are for the most part un¬ 
stable when exposed to the air. The best • method of 
operation is to prepare a strong solution (“ stock solution ”) 
of the required developer, and add it to the bath as may be 
required. Standing baths are freshened up by the addi¬ 
tion of J the quantity of developer used the first time. 

The developer usually used is beta-naphthol. Other 
developers in use are naphthylamine-ether (amido-naphthol 
ether), toluylene diamine, resorcin, phenol, alpha-naphthol, 
and Schaeffer’s salt. These developers are sold in various 
forms, as pastes, or powder, for example. They are also 


DIRECT COTTON COLORS 


i /3 


sold under different names, as blue developer, fast blue 
developer, etc. A few dyes are developed with a hot 
solution of soda. (See also p. 19.) 

Experiment 59. — (1) Dye a 10-gram skein of cotton yarn 
with 1 per cent diaminogene blue G, 20 per cent Glauber’s salt, 
and 2 per cent soda. Wash and remove a sample. Prepare a 
diazotizing bath with 1^ per cent sodium nitrite in 200 cc. water, 
to which 5 per cent hydrochloric acid is added, just before the 
skein is entered. Work cold 15 minutes, squeeze, and enter im¬ 
mediately in the developing bath of 0.3 per cent beta-naphthol 1 
in 200 cc. water. Work cold 15 minutes, wash and dry. 

(2) Dye with 6 per cent diazo black BHN, 20 per cent salt, 
and 5 per cent soda. Save sample. Diazotize and develop as 
directed above, using 2\ per cent sodium nitrite, 8 per cent 
hydrochloric acid, and 1 per cent beta-naphthol. 

(3) Dye with 5 per cent cotton brown A and 20 per cent 
Glauber’s salt. Save sample. Diazotize and develop, using 2\ 
per cent sodium nitrite, 8 per cent hydrochloric acid, and 1 per 
cent beta-naphthol. 

Test fastness of colors to washing (Exp. 7) and boiling water 
(Exp. 6) before and after diazotizing and developing. 

Experiment 13 also illustrates the method of diazotizing 
and developing. 

Application. — Diazotizing and developing are used for 
the production of red, blues, and black, with a high degree 
of fastness to washing. 

Loose cotton in nets may be placed in a vat con¬ 
taining the diazotizing liquid, lifted and allowed to 
drain, and placed in a rinsing vat, thence in the 
developer. 

Warps require a warp machine with three compartments, 

1 The beta-naphthol is dissolved with an equal weight of caustic soda. 


174 


PRINCIPLES OF DYEING 


each with its squeeze rollers. The best process is to pre¬ 
pare separate solutions of sodium nitrite and hydrochloric 
acid, add one-tenth to the diazotizing vat, and the remainder 
during the passage of the warp. The developer is added 
in the same way. The middle vat contains a rinsing 
liquor. 

Cloth is treated in a similar machine. 

Shading Developed Dyeings. — For obtaining the desired 
color with diazotized and developed dyes, the following 
methods may be employed : — 

(a) Simultaneous Dyeing with Several Diazotizable 
Colors. 

(b) By employing Mixtures of Various Developers. — Use¬ 
ful mixtures of this kind are : beta-naphthol and resorcin ; 
beta-naphthol and phenylenediamine; phenylenediamine 
and resorcin. 

Such developers as are applied in an acid bath cannot 
be mixed with such as are used in an alkaline bath. 

(c) Simultaneous Dyeing with Diazotizable and Non- 
diazotizable Colors. — In this case, the non-diazotizable 
color must not be affected in shade to any extent by the 
diazotizing process. The color which is unaffected by 
the diazotizing process is, however, not fast to washing, 
and is liable to bleed. 

(d) Topping with Basic Colors. — Like all other direct 
cotton colors, these colors can be combined with basic 
colors. 

Coupling.—The chemistry of coupling is the same as 
the chemistry of diazotizing and developing. In coupling, 
the diazonium compound is formed in solution instead of 


DIRECT COTTON COLORS 


175 


on the fiber, and then is combined with the dye. Parani- 
traniline is the only substance used in coupling. A cold 
solution of paranitraniline in hydrochloric acid is treated 
with sodium nitrite, and sodium acetate to neutralize excess 
of hydrochloric acid is added, and the dyed fabric is passed 
through the solution, as in diazotizing. The color will rub 
if all the hydrochloric acid is not neutralized. The solu¬ 
tion can be tested with a paper colored with Congo red, 
which is turned blue if any free hydrochloric acid is 
present. 

For details of the process see paranitraniline red (Chap¬ 
ter XIX). 

Experiment 60. — Dye a 10-gram cotton skein (boiled off) with 
5 per cent cotton brown A, 2 per cent soda, and 20 per cent 
Glauber’s salt in 200 cc. water, boiling half an hour. Remove a 
sample. Mix 2 per cent paranitraniline mixture 1 with 100 cc. 
water, and add 1.3 per cent sodium nitrite. Stir well. When all 
is dissolved, add 4 per cent sodium acetate, and work the yarn in 
the solution 20 minutes. Rinse and dry. 

After-treatment with Metallic Salts. — This increases 
fastness to light and washing. The salts used are copper 
sulphate, potassium bichromate, and chromium fluoride. 
With copper sulphate or chromium fluoride, copper or 
chromium salts of the color acid are probably formed, 
which are affected by light to a less extent than the sodium 
salt, and, being less soluble in water, do not bleed or wash 
out so readily. With bichromate of potash, the action is 
probably different; the color acid is oxidized to some 

1 Paranitraniline mixture. Heat 10 g. paranitraniline and 16 g. hydro¬ 
chloric acid (1.20 sp. gr.) in 400 cc. water until dissolved, and add 1800 cc. 
cold water. 20 cc. = 0.1 g. paranitraniline. 


176 


PRINCIPLES OF DYEING 


extent, and also converted into the corresponding chromium 
salt. 

As many direct cotton colors are altered considerably in 
shade by the after-treatment, it is necessary, in order to be 
sure of the ultimate result, to make laboratory dye-trials to 
determine what these alterations are, and make proper 
arrangements for producing the desired shade. For shad¬ 
ing , dyes must be used which are not changed by metallic 
salts. 

Application. —The dyed fabric is treated with a solution 
of the salts at the proper temperature, washed and dried. 
In warp dyeing, the salts are best added in portions during 
the passage of the warp. 

Experiment 61. — (a) Dye cotton yarn with 5 per cent diam¬ 
ine jet-black CR, 1 per cent soda, and 10 per cent Glauber’s salt 
in 200 cc. water, boiling half an hour. Wash, remove sample, 
and boil remainder 15 minutes with 4 per cent potassium bichro¬ 
mate in 200 cc. water. 

(b) Dye with 2 per cent Chicago blue 4 B, } per cent soda, 
and 5 per cent Glauber’s salt. Wash, remove sample, and boil re¬ 
mainder as above with 3 per cent copper sulphate in 200 cc. water. 

(c) Dye with 4 per cent benzo-chrome brown G and 5 per cent 
salt; wash, remove sample, and boil remainder 15 minutes with 3 
per cent copper sulphate, 3 per cent potassium bichromate, and 2 
per cent acetic acid in 200 cc. water. 

Test fastness of dyeings to washing and to boiling water, be¬ 
fore and after treating with metallic salts. Does the treatment 
affect the color of the yarn ? 

Defects in Dyeing. — Defects in dyeing direct cotton 
colors may be traced to insufficient preparation, or faulty 
manipulation. Spots, streaks, or stains may be due to oil 
spots, faulty wetting-out, defects in bleaching, or to not boil- 


DIRECT COTTON COLORS 


177 

ing for a sufficient length of time in the dye bath. Direct 
cotton colors, as a rule, yield good dyeings very easily. 

Sulphur Colors. — The sulphur colors are a group of 
direct-dyeing cotton colors (mostly black and brown) made 
by fusing various organic bodies with sulphur and alkalies. 
They are characterized by a high degree of fastness to 
light and washing, and are becoming of great importance. 

Properties. — The sulphur colors are, as a rule, insoluble 
in water, and are dissolved with the aid of sodium sulphide. 
The dye probably exists in a reduced form in the bath, and 
is afterward oxidized on the fiber. The oxidation often 
takes place on the surface of the liquid with the formation 
of a scum. Most sulphur colors are precipitated from 
solution by copper, so that copper cannot be used in dye- 
vats. Iron or lead pipes and iron or wooden rollers are 
used. • Most sulphur colors require an after-treatment to 
develop the color. 

The tinctorial power of these dyes is low, as they require 
from 10 to 50 per cent to produce full shades. They have 
recently been prepared in more concentrated forms, 4 to 5 
per cent producing a full black. 

Sulphur colors are used mainly on cotton. The dyes 
have no great affinity for the fiber, and standing baths 
should be used. 

Sulphur colors are oxidized and injured if exposed to 
the air. They must be kept dry, and in well-closed 
vessels. 

Sodium sulphide occurs in two forms : as the crystallized 
salts, and as the fused salt, the latter being about twice as 
strong as the former. 


N 


i/8 


PRINCIPLES OF DYEING 


Methods of Dyeing. — The dye should be dissolved very 
carefully in hot water, with the addition of sodium sulphide 
if necessary. The bath is prepared with the necessary 
salts and the color solution added, and the dyeing con¬ 
ducted at or near the boil. As a rule, the bath should be 
kept as a standing bath, since large quantities of the color 
usually remain in it. The sodium sulphide is gradually 
oxidized by the air ; a sufficient quantity of it should be 
used to keep the bath free from particles of undissolved 
dye. If too little sodium sulphide is present, the liquid is 
turbid, and particles of dye are seen if liquor is dropped on 
blotting paper. If too much is present, the dyeing lacks 
depth. 

Certain sulphur colors require hardly more precaution in 
dyeing than ordinary direct cotton colors. Others require 
careful protection of the goods from the air, to prevent 
superficial oxidation of the color. However dyed, the 
goods must be squeezed free of the excess of dye liquor as 
soon as they are removed from the bath, and carefully 
rinsed ; otherwise the color contained in the dye liquor will 
be oxidized and fixed superficially, with the result that the 
dyeing will rub. 

Machines or vats for dyeing with most sulphur colors 
must not contain brass or copper. Skeins are hung on bent 

iron rods \_/ , so that they are completely immersed 

in the bath, and can be turned without being lifted above 
the surface of the liquid. Warps are dyed in the usual 
form of machine, provided with iron or wooden guide 
rollers which are completely immersed in the liquid. Cloth 
is dyed on the jigger, or the hawking machine; it must 
pass between squeeze rollers, and be washed as soon as it 
leaves the dye-vat. 


DIRECT COTTON COLORS I 79 

After-treatment. — Most sulphur colors require an after- 
treatment. The methods used are: — 

( a) Oxidation by 

(1) Potassium bichromate; 

(2) Hydrogen peroxide; 

(3) Steaming and exposure to the air. 

( b ) Treatment with copper sulphate. 

The methods are illustrated by the following experiment. 

Experiment 62.— Dye three 10-gram skeins of cotton yarn 
(wetted-out) as follows : — 

(1) Mix 2 g. sulphur-black T with 2.5 per cent caustic soda 
and 4 g. sodium sulphide in 60 cc. water, and boil until dissolved. 
Dilute to 200 cc., and add 1 per cent soda and 10 g. Glauber’s 
salt. Boil the yarn in this solution for 30 minutes. Wash well and 
dry. Save the bath. 

(2) Mix 2 g. immedial blue C with 8 per cent soda and 8 per 
cent sodium sulphide in 100 cc. water. Boil until dissolved, dilute 
to 200 cc., and add 5 g. salt. Enter the skein and boil 30 min¬ 
utes. Save the bath. This dye requires an after-treatment. Rinse 
the skein and develop the color in a cold bath of 10 cc. hydrogen 
peroxide 1 and 10 cc. ammonia in 200 cc., working 10 minutes. 

(3) Mix 3 g. autogene black, 7 per cent salt, and ^ per cent 
sodium carbonate with 200 cc. water, heat until dissolved. Enter 
the yarn and boil 30 minutes. Remove and wash. Save the bath. 

Test fastness of all three skeins to washing and to boiling water. 
Place 2 or 3 g. of copper in each dye-bath, after it has been used, 
and boil 15 minutes. Examine bath and copper. What effect has 
the copper? 

Soaping.—A soaping, after completing the dyeing with 
sulphur colors, has two objects : — 

1 Hydrogen peroxide, i| volumes commercial diluted to 10. Ammonia 
\\ volumes diluted to 100. 


i8o 


PRINCIPLES OF DYEING 


(1) It neutralizes mineral acids which have not been 
completely washed out. 

(2) It softens the goods, and removes loosely adherent dye. 

Defects in Dyeing. — For perfect dyeing with sulphur 
colors, the following are essential: — 

(1) Careful Solution. — The dye liquor should be clear, 
and kept clear by the addition of sodium sulphide if 
necessary. 

(2) Squeezing immediately after removal from dye-bath, 
to press the liquor out uniformly. It has a tendency to 
collect at the edges of cloth. 

(3) Careful rinsing , immediately after dyeing, to remove 
the excess of dye liquor; and after after-treatment, to 
remove all traces of acids. 

If not properly applied, sulphur colors may tender the 
goods, or be defective in appearance. 

Tendering .—Tendering may be traced to insufficient 
washing of the goods, or to exposure to the air while dye¬ 
ing. Any sodium sulphide left on the material will be 
gradually oxidized, and under some circumstances, as 
exposure to the air, free sulphur is precipitated on the 
goods, which is gradually oxidized to sulphuric acid. 
Tendering may be prevented by the addition of sodium 
acetate to the last wash water; it will neutralize the 
mineral acid, with the formation of acetic acid, which 
will not injure the goods. 

Tendering may also be traced to over-oxidation during 
the after-treatment with potassium bichromate, or insuffi¬ 
cient removal of the mineral acid used in the after- 
treatment. 


DIRECT COTTON COLORS l8l 

Bronzy appearance of goods dyed with sulphur colors 
is due to improper manipulation in the dye-bath, with 
exposure to air during dyeing. Rubbing off of the color 
is due to the same cause. 

Topping Direct Cotton Colors with Basic Colors. — The 

direct cotton colors, whether after-treated or not, have the 
power of combining with basic colors. This property is 
utilized for shading direct cotton colors, as well as, to some 
extent, for dyeing basic colors. It will be discussed in 
detail under that head. Sulphur colors may be topped 
with basic colors, with the production of quite fast dyeings. 

Fastness of Direct Cotton Colors. — The direct cotton 
colors, with the exception of the sulphur colors, bleed into 
white cotton, unless they are after-treated, even though 
they often lose little color in washing. Some of them are 
sensitive to acids, particularly the reds. When properly 
dyed, rubbing off is out of question. Dyeings diazotized 
and developed or after-treated, are very fast to washing. 

Application to Linen. — Direct cotton colors do not pos¬ 
sess the requisite degree of fastness for application to 
linen. After-treatment renders them sufficiently fast. 
The methods are the same as for cotton. Sulphur colors 
are used to a considerable extent on linen. 

Application to Wool.—The direct cotton colors are not 
employed to a large extent for wool, as the acid dyes are 
much cheaper. Some of them possess an excellent fast¬ 
ness to milling. They are used largely in dyeing union 
goods (cotton and wool). 

They are applied to wool in neutral baths, with or with- 


182 


PRINCIPLES OF DYEING 


out the addition of common salt or Glauber’s salt. In 
some cases, wool is dyed with these colors in a bath 
acidified with acetic acid, and, if necessary, the color 
is then developed in a weak solution of soda. 

Application to Silk. — Some of the direct cotton colors 
are of excellent fastness to water, washing, and milling 
on silk. 

The colors are applied in a soap-bath acidified with 
acetic acid. Enter at 45 to 6o° C., bring almost to a boil, 
and after handling three-quarters of an hour, add 2 to 
4 per cent acetic acid, and exhaust the bath slowly. Rinse 
and brighten. 

After-treatment. — When great fastness is required, 
these dyes may be after-treated on silk with metallic 
salts or by diazotizing and developing. The methods 
used are practically the same as for cotton. An exces¬ 
sive amount of metallic salts may cause damage. 

After developing, the silk is passed through sulphuric 
acid to brighten. To produce the best results, the silk 
should be soaped in a boiling hot soap-bath after develop¬ 
ing, then rinsed and brightened. 


CHAPTER XVI 


BASIC COLORS 

t 

The basic colors are salts of organic color bases, and, as 
we have seen in the case of fuchsine, they are direct colors 
for wool and silk, but dye cotton only with the aid of a 
mordant. The basic colors are the oldest artificial colors 
known. The first number of the group, discovered in 
1856, was the first artificial dye manufactured. 

Composition. — The basic colors are generally sold in the 
form of their hydrochloric acid salts, but some are brought 
into commerce as acetates, oxalates, sulphates, nitrates, or 
as double salts of hydrochloric acid and zinc chloride; in 
rare cases in the form of the free color base. They are 
sold as pastes, powders, or crystals, the latter being the 
most concentrated form. In some cases the crystals are 
very nearly pure, while as a rule the powders or pastes 
are purified to a less extent. 

Properties. — Most of the basic colors are soluble in 
water, while all dissolve in alcohol. Generally they re¬ 
quire about 250 times their weight of hot water for so¬ 
lution. A few, such as auramine, are decomposed by hot 
water. 

Hard water with temporary hardness acts upon these 
dyes by throwing down the color base in the form of a 
curdy precipitate, thereby rendering a part of it useless 
for dyeing purposes; while further injury may be caused 

183 


184 


PRINCIPLES OF DYEING 


by the precipitate being deposited on the goods, giving 
rise to spots and unevenness, dye-spots. 

Hard water may be corrected by the addition of suffi¬ 
cient sulphuric or acetic acid to decompose the carbonates 
(see Chapter XIII). 

The basic dyes possess great tinctorial power, and pro¬ 
duce full shades with very small amounts of dye. They 
are characterized by their brilliancy and purity of hue. 

Application to Cotton. — Basic colors are dyed on cotton 
by several methods : — 

(1) Direct Dyeing. — A few basic dyes are used for pro¬ 
ducing delicate tints on bleached cotton. 

(2) Tannin Mordant. — The cotton is mordanted with 
tannic acid, which is fixed by means of salts of antimony 
or iron, and then dyed. 

(3) Aluminium Mordant. — Aluminium hydroxide acts 
as the mordant. This is rarely used. 

(4) Dyes as Mordants. — Direct cotton colors here serve 
as mordants for the basic dyes. This process is assuming 
greater importance every year. 

(5) Turkey-red Oil Mordant. 

Tannic Acid. —Tannic acid is used as a mordant for 
basic colors in several forms : — 

(1) As sumac, or gallnuts. 

(2) As extracts, more or less purified, of gallnuts, 
sumac, or myrabolans. 

(3) As purified tannic acid. 

Sumac consists of the leaves and twigs of several species 
of Rhus. It is sold in the form of the whole or crushed 
leaves, or as a powder; the leaf-stalks and small twigs are 


BASIC COLORS 


185 


often admixed. The value of sumac depends upon its 
content of tannic acid, which may vary considerably. 
Best sumac contains 15 to 20 per cent tannin, and has an 
olive-green color, and a fresh, agreeable odor. Sumac 
dull in color and odor has been deteriorated by moisture 
and long keeping. Sumac contains some reddish coloring 
matter, which is taken up by cotton along with the tannic 
acid. Hence it cannot be employed in the dyeing of light 
and brilliant shades. Purchases of sumac should be based 
upon a guaranteed content of tannic acid and low amount 
. of coloring matter. 

Gallnuts are the excrescences on oak trees, caused by 
certain insects. The best gallnuts contain 55 to 60 per 
cent tannic acid. Chinese and Japanese gallnuts (from 
Rhus) may contain 65 to 70 per cent. 

Myrabolans are the fruit of several kinds of trees grow¬ 
ing in China and the East Indies. They contain much 
coloring matter. 

Chestnut extract is a dark-colored extract from chestnut, 
and is used in the black dyeing, and weighting of silk. 

Extracts . — Ordinary sumac extract occurs as a thick, 
dark-brown liquid, containing the tannic acid and color¬ 
ing matter of the sumac. In the decolorized extract, the 
coloring matters have been removed. Decolorized extract 
can be used even for light shades. Purchases should be 
based upon actual content of tannic acid. Myrabolans 
extract is similar to sumac. Gallnut extract is purer, and 
comoares with the decolorized sumac extracts. 

I 

Tannic acid , C 14 H 10 O 9 + 2 H 2 0 , is prepared from gall- 
nuts. The gallnuts are extracted with water or a mixture 
of water, alcohol, and ether, the aqueous solution separated, 


PRINCIPLES OF DYEING 


186 

evaporated, and purified. Tannic acid occurs as ( a ) a color¬ 
less amorphous mass, ( b ) light yellow to buff-colored scales, 
(c) brittle vitreous masses. It is soluble in 6 parts of cold 
water, and more readily in hot water. Its solubility is de¬ 
creased by sulphuric or hydrochloric acid, sodium chloride, 
and some other salts, and it can be precipitated (salted out) 
from strong aqueous solution by these substances. 

A solution of tannic acid in water decomposes gradually 
on standing. An addition of borax hinders this change. 
It is easily oxidized and acts as a reducing agent. Its 
alkaline solution rapidly absorbs oxygen from the air, and 
becomes brown. 

Salts. — Most of the salts of tannic acid are insoluble in 
water, but are easily soluble in acids. It is difficult to pre¬ 
pare them in the pure state. 

Hard Water . — The quantity of tannic acid extracted 
from sumac by water decreases as the water grows in 
hardness, while the quantity of the non-tannin matters 
increases. In one instance with a very hard water, only 9 
per cent of the tannic acid in the sumac was extracted. 
Hard water should not be used for preparing mordant 
baths with sumac. 

Affinity for Cotton. — The affinity of cotton for tannic 
acid varies according to the conditions, as follows : — 

(1) The more concentrated the solution, the greater the 
quantity of tannic acid absorbed by the cotton. 

(2) The longer the cotton and solution remain in con¬ 
tact, the more tannic acid is absorbed. In six hours, 
nearly four times as much tannic acid was absorbed as 
in an hour. 


BASIC COLORS 


187 


(3) The lower the temperature of the solution, the greater 
the quantity absorbed. Cotton took up 17 times as much 
tannic acid from a cold solution as from a boiling one. 

(4) The addition of salts causes more tannic acid to be 
taken up. 

Under very favorable conditions, cotton absorbs only 30 
per cent of the tannic acid in solution. Considerably less 
is usually taken up in practical work. As far as possible, 
a standing bath should be used for mordanting with tannic 
acid. 

Antimony Salts. — The salts of antimony used in fixing 
tannic acid are as follows : — 

Antimony potassium tartrate , or tartar emetic, 2 K(SbO) 
C 4 H 4 0 G -b H 2 0 , is the principal salt of antimony used in 
dyeing. It is not very soluble in water, and should contain 
43 per cent Sb 2 0 3 . 

Antimony sodium fluoride , NaSbF 4 , is readily soluble in 
water, and 66 parts are equal to 100 parts tartar emetic. 

Antimony salt (Hae?i), SbF 3 (NH 4 ) 2 S 0 4 , is a double salt 
of ammonium sulphate and antimony fluoride. 

Double oxalate of antimony and potassium , SbK 3 (C 2 0 4 ) 3 . 

Mordanting with Tannic Acid. —Two methods are in 
use : — 

(1) Loose cotton and yarn are entered in a hot or boil¬ 
ing bath containing the necessary quantity of tannic acid, 
worked well, and soaked for 3 to 12 hours, or over night, 
while the bath cools. The material is squeezed or hydro- 
extracted, washed lightly, and the tannic acid fixed as de¬ 
scribed below. 

(2) For warps and piece goods a stronger solution of 


188 


PRINCIPLES OF DYEING 


tannic acid (2 0 to 3 0 Tw.) is used. They are run through 
the warm solution, squeezed, and fixed after they have 
stood some hours. 

The strength of the tannin liquor to be used depends on 
the depth of the color desired. The baths are used con¬ 
tinuously ; exhaustion is aided by the addition of salt. 

Fixing Tannic Acid. — Two methods of fixing are gener¬ 
ally used, namely, with antimony and with iron. 

Antimony. — The process is very simple. The mordanted 
cotton is passed into a bath of \ to 3 per cent of tartar 
emetic, or corresponding amounts of other antimony salts, 
at 30° to 50° C. The baths are used continuously, their 
strength being restored from time to time, while the acid 
produced in the fixing process is carefully neutralized with 
soda, or chalk may be added to the bath for the same pur¬ 
pose. The cotton must be washed very carefully after 
fixing, as superficially fixed antimony will not only give 
rise to rubbing of the color, but may produce blood-poison¬ 
ing if it comes in contact with the skin. For some colors 
a soaping before dyeing is necessary. 

Iron. — Iron salts can be used only for dark shades. 
The fixing-bath is prepared with copperas (ferrous sul¬ 
phate) or “ nitrate ” of iron, with the addition of some 
chalk to neutralize the acid which is liberated during the 
fixing process. 

Dyeing. — The dyeing is conducted in a cold or warm 
bath, and the solution of the color is added in several por¬ 
tions to insure level dyeing. The time required is 30 to 60 
minutes. Hard water is neutralized with acetic acid. If 
the color is apt to dye uneven, the addition of some acetic 


BASIC COLORS 


189 


acid will cause it to go on the fiber more slowly and evenly. 
Undissolved particles of color will cause dye-spots. The 
bath should be exhausted. 

Experiment 63. — In mordanting and dyeing, work carefully so 
that the mordant and dye will be taken up evenly. These dyes are 
not as easily applied as the direct cotton colors. See that your 
boiled-off skeins are thoroughly wetted out. 

Mordanting .—Work 8 boiled-off skeins of cotton yarn in a clear 
solution of 5 g. tannic acid in 1000 cc. water for 15 minutes, and 
allow to stand half an hour, working occasionally. Squeeze. Fix 
the tannic acid by working 5 minutes in a bath of 2 g. tartar emetic 
in 1000 cc. water, and allow the skeins to remain in this bath 15 
minutes, or until you are ready to dye them. 

Dyeing. — Make up a bath of per cent acetic acid and ^ per 
cent chrysoidine R in 200 cc. water; enter a skein and work care¬ 
fully 5 minutes ; raise the temperature to 50° and remove the flame. 
Allow the skein to remain in the bath half an hour, working from 
time to time. Wash. 

Dye a second skein with J per cent methyl violet 5 B; a third 
with V per cent cresyl blue; a fourth with 1 per cent malachite 
green; a fifth with \ per cent brilliant saffranine; a sixth with 
1 per cent brown JE; a seventh with per cent crystal violet; 
an eighth with 1 per cent auramine. Use in each case \ per 
cent acetic acid, and follow directions above given. Test fastness 
of all skeins to washing. 

Janus Colors. — The Janus colors may be applied like 
ordinary basic dyes. Another method is recommended : 
the material is dyed at a boil with salt and sulphuric acid, 
then fixed in a boiling bath of sulphuric acid, tartar emetic, 
and tannic acid. 

After-treatment with Tannic Acid. — The fastness of the 
dyeings are increased by an after-treatment with tannic 


PRINCIPLES OF DYEING 


190 

acid. After dyeing, the goods are passed through a bath 
of 2 per cent tannic acid, and rinsed thoroughly. 

Mordanting with Turkey-red Oil or Soap. — This process 
gives very bright colors, but not at all fast. It is little used. 
The goods are soaked in a bath of Turkey-red oil or soap, 
dried and worked in a bath of aluminum acetate, washed 
and worked again in soap; finally washed and dyed as 
described above. 

Alum Mordant. — This gives bright though fugitive 
shades. The goods are treated in a boiling bath of about 
| oz. alum per gallon water, and then passed through a 
tepid bath of soda, wrung out, dried, and dyed. The soda 
precipitates aluminium hydroxide on the fiber, which acts 
as a weak acid. 

Dyes as Mordants. — The use of basic colors to top other 
dyestuffs, especially direct cotton colors, is very important. 
The color base of most basic colors has the property of 
uniting with the color acid of direct cotton colors, forming 
insoluble compounds. The basic color is thus fixed fast to 
washing. The compound is, in many cases, decomposed if 
it is heated above 70°. Numerous compound shades may 
be produced by topping direct cotton colors with basic 
colors, and by combining basic colors with other dyes for 
which they have some affinity. They are used to brighten 
the color of alizarin, logwood, and aniline black. 

The operation of topping is very simple. The material 
is worked in a cold or warm bath of the dye for about half 
an hour. It is then rinsed and dried. 

Experiment 64. — Dye with 2 per cent thioflavin S as directed 
in Exp. 58, and top with ^ per cent malachite green (Exp. 63). 
Test fastness to washing. 


BASIC COLORS 


IQI 

Fastness of the Colors. — The basic colors on cotton are 
not very fast to washing, though they do not bleed. They 
are, as a rule, not very fast to light. 

Defects in Dyeing. — Dye-spots are caused by undissolved 
particles of the dye, or precipitation of the color base by 
hard water. 

Rubbing is due to incomplete washing after mordanting 
and before dyeing. 

Uneven dyeing is caused by uneven mordanting, or too 
rapid absorption of the dyestuff. Addition of acetic acid 
to the bath causes the dye to be absorbed less rapidly. 

Stripping. — Basic colors may be stripped from the fiber 
* by boiling with dilute sulphuric acid. 

Basic Colors on Wool. — Wool does not have so great 
affinity for basic dyes as for acid dyes; consequently it is 
less difficult to produce level shades with basic dyes. The 
wool plays the part of an acid, combining with the color 
base to form a lake. 

Dyeing. — Basic dyes are applied to wool in a neutral 
bath, or in a bath made slightly acid with acetic acid. 
Acetic acid prevents spotting due to precipitation of the 
free color base. An excess is to be avoided, as it retards 
the exhaustion of the bath. Basic dyes are sometimes 
dyed with the addition of soap, which increases the brill¬ 
iancy of the shade. In dyeing with certain green dyes, 
the wool is mordanted with sulphur. 

The dye should be dissolved in hot water, and added to 
the dye-bath through a cloth filter. If the water is not 
pure, its hardness should be corrected with acetic acid. 


192 


PRINCIPLES OF DYEING 


The two methods of dyeing are as follows: — 

First Method. — The bath is made slightly acid, and the 
color solution added. If the color is apt to dye uneven, 
the wool is entered at a moderate temperature, otherwise 
it is entered into the boiling bath. After 15 to 30 minutes 
at or near the boil, the temperature is allowed to fall to 
from 6o° to yo°, the wool is taken out and washed without 
much delay and dried. 

Second Method. — The water is boiled well with 2 to 4 
per cent soap, the sticky scum removed, and the color 
solution added. The dyeing proceeds as by the first 
method. The bath is not exhausted, and is used con¬ 
tinuously. 

Experiment 65. — Dissolve 1 per cent methyl violet 6 B in 200 
cc. water, enter a 5-gram skein of wool and boil half an hour. Is 
the bath exhausted? 

Dye skeins with 1 per cent methyl violet 4 R, 

1 per cent malachite green, 

1 per cent Bismarck brown, 

1 per cent thionine blue, 

1 per cent saffranine M, 

1 per cent wool blue, 

1 per cent auramine. 

Test fastness to washing. 

Sulphur Mordant. — Brighter and faster dyeings with 
malachite green and brilliant green are obtained on a 
sulphur mordant. The method is illustrated by the fol¬ 
lowing experiment: — 

Experiment 66. — Dissolve 20 per cent sodium thiosulphate, 
10 per cent alum, and 4 per cent sulphuric acid in 200 cc. water. 
Enter a 5-gram skein of wool, heat to 75 0 C., and keep near this 


BASIC COLORS 


193 


temperature for half an hour. The thiosulphate is decomposed, 
sulphur separates in a finely divided form, and is absorbed by the 
wool. Dye the mordanted skein and an unmordanted skein in the 
same bath with 2 per cent malachite green. Test fastness to 
washing. 

Fastness of the Colors. — The following are the charac¬ 
teristic features of the colors produced on wool by means 
of the basic dyes : great brilliancy of shade, evenness of dye, 
good penetration, marked rubbing off, want of fastness to 
light, moderate fastness to washing, and a great tendency 
to bleed. 

Defects. — Dye-spots are caused by precipitation of the 
color base in the dye-bath by hard water, or by imperfect 
solution of the dye. 

Basic Colors on Silk. — Silk has a greater affinity for 
basic dyes than wool, and gives faster colors. 

Silk is dyed in a neutral or alkaline bath, or one slightly 
acidified with acetic, tartaric, or sulphuric acid. Usually 
soap or boiled-off liquor is added to the dye-bath. The 
general process is as follows: — 

The bath is made up with 1 to 2 per cent soap, or 10 to 
30 per cent boiled-off liquor, then acetic acid is added until 
the alkaline reaction has almost or entirely disappeared, 
and finally the carefully dissolved dyestuff is added. The 
silk is entered at 30 to 40° C.; the temperature is raised to 
near the boil, while continually handling the material, the 
dyeing being completed at 80 to 90° C. The process is 
accelerated by raising the temperature and by having the 
dye-bath weakly alkaline ; on the other hand, it is retarded 
if the bath is kept slightly acid. 


o 


194 


PRINCIPLES OF DYEING 


The dyeing process may be regulated by varying the 
acidity of the bath. In the case of full, deep shades, the 
bath is kept as neutral as possible, in order to utilize the dye¬ 
stuff to its fullest extent, since the large quantity of dye 
present will insure the even dyeing of the silk. With pale, 
delicate shades, it is customary to work with a slight excess 
of acetic acid in the bath, to prevent the fiber from taking 
up the color too rapidly, and to insure that it will be evenly 
dyed. 

After dyeing, the silk is brightened. 

After-treatment. — The fastness to washing of the basic 
colors on silk can be greatly improved by an after-treatment 
with tannic acid and tartar emetic. 

The dyed silk is best kept over night at 48 to 6o° in a 
tannin bath containing 1 per cent pure tannic acid, then 
fixed at 6o° without rinsing in a bath of 8 oz. tartar emetic 
per 10 gal. water, rinsed, soaped, and brightened. 

For less brilliant shades, sumac may be employed in 
place of tannic acid. 


CHAPTER XVII 


ACID COLORS 

Acid colors possess a distinctly acid character, and are 
dyed on the animal fibers as the free color acid. With the 
exception of picric acid, the acid colors are sold as salts, 
mostly alkali salts, but a few in the form of lime salts. 

Properties.—With few exceptions, the acid colors dis¬ 
solve readily in hot water, requiring about 25 to 50 times 
their weight of water for solution. Hard water is not very 
injurious in dyeing wool with these colors, as the lime salt 
of the dye is decomposed by the acid added to the bath. 
However, it is best to use distilled water. The acid colors 
do not possess great tinctorial power. About 3 per cent 
of color is usually required for a full shade on wool. 

Application to Cotton. — The dyeings with acid colors on 
cotton do not possess any fastness to water and washing. 
As they are not sensitive to acids, and some of them are 
faster to light than the direct cotton colors, they find a 
limited application on some classes of material which do 
not require to be washed. 

Methods of Dyeing. — The dye-bath should be as con¬ 
centrated as possible in order to produce full shades. It is 
never exhausted by the cotton, but is used continuously as 
far as possible. 

The methods of dyeing acid colors on cotton are 
illustrated by Experiment 23, Chapter IV (which see). 

195 


196 


PRINCIPLES OF DYEING 


They are usually applied with the alum mordant in the 
dye-bath. 

Application to Jute. —Acid colors are dyed on jute with 
the addition of 2 \ per cent oxalic acid or alum. For some 
colors, the basic alum mordant used for cotton may be used 
(Exp. 23). 

Application to Wool. — The acid dyes are used to a great 
extent on wool, both on account of their cheapness and 
for the reason that they are easily applied. 

The process of dyeing with acid colors on animal fibers 
is to be regarded as a salt or lake formation, in which the 
wool or silk acts the part of the base, while the color acid 
plays the part of the acid. The chemistry of the process 
has already been discussed. 

Methods of Dyeing.—The exact method for applying 
the acid colors to wool depends upon the nature of the 
material and its form, and the affinity of the dye for the 
fiber. 

Level-dyeing acid colors , or those which do not go on the 
fiber too rapidly, are applied as follows : — 

The bath is prepared with the necessary quantity of 
dye, 10 per cent Glauber’s salt, and 4 per cent sulphuric 
acid. The wool is introduced and worked continuously, 
while the temperature is raised to the boil. The dyeing is 
complete in 1 to 1J hours. In place of Glauber’s salt and 
sulphuric acid, 10 per cent bisulphate of soda may be used. 

In some cases, as with very loose yarns and with dyes 
which level easily, the wool may be entered directly into 
the boiling bath. 

For ordinary acia dyestuffs , or when the goods must not 


ACID COLORS 


197 


be allowed to take up the dye too rapidly (as in the case of 
warps, or heavy material), the following precautions are 
used: — 


The material is introduced in the bath at a low tempera¬ 
ture with a slight addition of acid, and the remainder of 
the acid is added in small portions to the boiling bath. 
The temperature must not be raised to the boil too rapidly. 

Special methods must be used for some dyes. The fol¬ 
lowing are examples : — 

Dye with 10 to 20 per cent Glauber’s salt and 5 per cent 
acetic acid. After boiling for some time, add 5 per cent 
sodium bisulphate, or 2 to 5 per cent sulphuric acid, which 
exhausts the bath. 

Dye with Glauber’s salt and acetic acid, and exhaust the 
bath by the addition of more acetic acid. 

Dye with Glauber’s salt and acetic acid alone. 

Dye with ammonium acetate. The bath slowly becomes 
acid by the decomposition of this salt. 

Experiment 67. — Prepare the bath with 1 per cent of the dye, 
10 per cent Glauber’s salt, and 4 per cent sulphuric acid. Enter 
the wool, heat to boiling, and boil 30 minutes. Observe if the 
bath is exhausted, and test fastness to washing. 

Dye 5-gram skeins with each of the following colors : — 


Skein No. 1. 

2. 

3 - 

4 - 

5 - 
6 . 

7 - 

8 . 


Fast red A extra. 

Indian yellow. 

Ponceau R. 

Acid violet 4 RS. 

Acid green BN. 

Wool blue R (use 3 per cent acetic acid instead 
of 4 per cent sulphuric acid). 

5 per cent wool black 4 B. 

Quinoline yellow. 


198 


PRINCIPLES OF DYEING 


Alkali Colors. — This is a special class of acid dyes, 
which must be applied in an alkaline bath, and the color 
developed afterward by treatment with an acid (see 
Exp. 24). The dye-bath is not exhausted. 

Experiment 68. — Dye a wool skein with \ per cent Nichol¬ 
son’s blue 4 B and 4 per cent borax in 200 cc. water, boiling half 
an hour. Remove a sample. Develop in a warm bath (50° C.) 
of 2 per cent sulphuric acid in 200 cc. Explain the change in 
color. Test fastness to washing. 

Level Dyeing. — Apart from imperfect preparation of 
the material, or faulty construction of the dye-vat, stripes, 
cloudiness, and imperfect penetration of acid dyes are 
caused by the absorption of the dyestuff by the wool too 
rapidly. 

The following circumstances favor level dyeing: — 

(1) Old dye liquors, i.e. baths which have been used 
several times for dyeing. 

(2) An increased amount of Glauber’s salt. The Glau¬ 
ber’s salt retards the absorption of the coloring matter, 
and it exercises a solvent action on the particles already 
attached to the wool, taking the dye from the darker 
portions of the material, and thus affording the lighter 
portions an opportunity for taking up the excess. An 
increased amount of Glauber’s salt is employed when 
dyeing pale shades, when dyeing thick, closely woven 
goods, and indeed whenever the dyeing appears irregular. 

(3) Regulating the amount of acid, or using weaker 
acids. The acid acts chemically upon the fiber, and also 
liberates the free color acid of the dye, which unites with 
the wool the more rapidly the more completely it has been 
set at liberty. The acid may be regulated (1) by using a 


ACID COLORS 


199 


smaller amount, (2) by using weaker acids, as acetic acid, 
(3) by adding the acid to the bath gradually and in small 
portions at a time. 

(4) Regulating the temperature. The higher the tem¬ 
perature of the dye-bath, the more rapidly is the coloring 
matter taken up by the wool. Hence, by raising the tem¬ 
perature of the bath slowly, the rate of dyeing can be 
lowered. Some few dyes dye more level shades if the 
goods are entered at the boil. 

Mixing.—Acid dyes may be mixed in every proportion. 
It is best to mix colors which require the same methods of 
application; otherwise the dyeing process must be that 
required by the least easily leveling color. 

For shading , or color matching , the additions to the bath 
should always consist of easily leveling dyestuffs. 

Exhaustion of Bath. — The acid dyes are always ex¬ 
hausted (or nearly so) from the bath by wool, with the 
exception of alkali blues, which are dyed in a standing bath 
where possible. 

Defects in Dyeing. —The following irregularities may be 
met with in dyeing wool with acid dyes : — 

(1) Dye spots, i.e. deeply dyed spots or specks on the 
goods. 

(2) Irregular dyeing, as cloudiness, dark or light streaks, 
and pieces not dyed through, that is, the surface of the 
cloth is darker than the interior. 

( 3 ) Speckled goods. 

(4) Rubbing off of the color. 

Dye-spots are sometimes due to defective scouring and 
washing of the material. Dye-spots are liable to occur 


200 


PRINCIPLES OF DYEING 


when the color acid of the dyestuff employed is sparingly 
soluble, or insoluble, especially if it tends to become 
resinous or tarry in the hot dye-bath, forming sticky glob¬ 
ules which adhere to the wool. 

In preventing dye-spots, the aim is to precipitate the 
color acid in as fine a state of division as possible, and 
through the whole bath, so that the particles remain sepa- • 
rate, and gradually dissolve in the bath without combining 
to form globules. 

Dye-spots may be prevented : — 

By dissolving the dyestuff in boiling water, filtering, and 
pouring it gradually in the bath. 

By adding the acid or bisulphate of soda to liberate the 
color acid after the goods have been boiled in the dye-bath 
with the dye for some time. 

Dye-spots are sometimes formed when a new bath is 
charged with Glauber’s salt, sulphuric acid, and dye at the 
ordinary temperature, by the bubbles of air expelled from 
the water when it is heated carrying particles of color acid 
to the surface, where they form a scum which produces 
dye-spots on the goods. If, after charging with sulphuric 
acid and Glauber’s s'alt, the bath is heated to a boil, and 
the color solution then added, no scum is formed, since 
the gases have been expelled. 

Irregular dyeing is due to too rapid combination of dye 
and fiber, and is to be prevented by taking the precautions 
already given for level dyeing. 

Speckled Dyeing. — Some dyes have a greater affinity for 
one end of a wool fiber than for the other. This form of 
irregular dyeing gives a speckled appearance to the goods. 
The defect may be lessened somewhat by using the pre- 


ACID COLORS 


201 


cautions for level dyeing, but in some cases the dye must 
be discarded. 

Experiment 69. — Prepare a bath with 7 per cent nigrosine 
S.I.W. (soluble in water), 10 per cent Glauber’s salt, and 1 per 
cent acetic acid. Enter a 5-gram skein of wool, boil 20 minutes, 
remove, and add 4 per cent acetic acid. Again enter the wool, 
and boil 20 minutes. Is the color uniform? Explain. 

Rubbing . — Certain acid colors are prone to rub, if the 
dye-bath is not exhausted. For these colors, an excess of 
dyestuff in the bath must be avoided. 

Fastness. —The acid dyes vary considerably in fastness. 
Some of them are very fast to light and washing, but many 
of them bleed in milling. 

Acid Dyes on Silk. — Silk does not possess as great an 
affinity for acid dyes as does wool; many acid dyes are 
removed from silk even by washing with water. 

Methods. — Silk is dyed in a bath of boiled-off liquor, or 
soap made acid (broken) with sulphuric acid. Boiled-off 
liquor gives the best results. The methods of producing 
level colors are : — 

(1) Increasing the proportion of soap or boiled-off 
liquor. 

(2) Diminishing the amount of sulphuric acid, or using 
a weaker acid. 

(3) Regulating the temperature of the bath. 

Alkali Colors. — With these dyes, the silk is dyed in a 
soap-bath, sometimes with the addition of soda or borax, 
and the color is afterward developed as in the case of 
wool. 


CHAPTER XVIII 


MORDANT DYESTUFFS 

Mordant dyestuffs are acid bodies which are always 
fixed upon the fiber in the form of insoluble metallic salts. 
The most important and fastest natural dyes belong to this 
group, and also many of the most important artificial 
colors. The lakes in which the mordant dyes are fixed 
upon the fiber are often very complex in composition. 

Mordant dyestuffs form insoluble calcium salts, so that, 
in many cases, hard water is injurious in dyeing with them. 

Methods of Application. — The mordants used for these 
dyes consist of salts of iron, chromium, and aluminium. 
Three general methods of application are in use: — 

(1) Mordanting and dyeing , used for cotton and wool. 
The goods are mordanted first, and then dyed. The mor¬ 
dant is fixed on cotton in various ways. Wool boiled in 
dilute solutions with metallic salts decomposes them, and 
when afterward brought in contact with the dyestuff, the 
metallic oxides held in the wool fiber combine with it to 
form colored lakes. 

(2) Single-bath method , used for cotton and wool. The 
dyestuff and mordant are mixed in the same bath, and the 
color-lake is gradually formed, and absorbed by the fiber, 
in the manner of a direct dye. 

(3) Dyeing and mordanting , used only on wool. The 
principle of this process is, that certain mordant dyes 


202 


MORDANT DYESTUFFS 


203 


possess such highly acid properties that they may be dyed 
upon wool in the same way as acid dyes, and the color-lake 
is afterward formed by application of the mordant in the 
same or a different bath. Dyes belonging to this group 
are called acid-mordant colors. 

Natural Mordant Colors. — Most of the natural dyestuffs 
are members of this group. The more important are log¬ 
wood, fustic, and cutch. They occur in commerce as the 
raw materia], and as liquid or solid extracts. 

Artificial Mordant Dyestuffs. — These dyes occur as : — 

Powders , generally soluble in 20 to 50 times their 
weight of water. Some of the powders are compounds 
of insoluble mordant colors with sodium bisulphite, and 
must be dissolved in cold water, as hot water decomposes 
them. 

Pastes , consisting of the dyestuffs in a finely divided 
form, mixed with water. They must not be allowed to dry 
up or freeze, as they thereby become less soluble. Vessels 
not perfectly closed may be covered with a damp cloth 
moistened with glycerol, to prevent evaporation. Pastes, 
damaged by drying or freezing, can be restored as follows : 
Dissolve in caustic soda, precipitate with a slight excess of 
sulphuric acid, wash the precipitated dye, and dilute with 
water. 

Mordant Colors on Cotton.—The methods of applying 
mordant dyestuffs to cotton and wool are so entirely differ¬ 
ent that it is best to treat the two separately. 

One of the mordant dyestuffs most important in cotton 
dyeing is alizarin. 


204 


PRINCIPLES OF DYEING 


Alizarin. —The use of madder root for dyeing has come 
up to us from the ancients. In 1826, madder was found 
to contain two coloring principles, alizarin and purpurin; 
in 1868, Graebe and Liebermann discovered their composi¬ 
tion, and prepared both of them from anthracene, a hydro¬ 
carbon found in coal tar. Since then, artificial alizarin has 
driven madder root almost completely from commerce. 

Alizarin, C 14 H 8 0 4 , occurs as a reddish yellow powder, or 
as bright orange-red needles, or as a paste with water. It 
is almost insoluble in cold water, and very slightly soluble 
in hot water, but it dissolves readily in alcohol or ether and 
some other solvents. It dissolves in caustic soda, forming 
a sodium salt of a blue-violet color; also in ammonia 
(ammonium salt) with a purple color. Acids decompose 
these salts, and precipitate the alizarin. Like other 
dyes, it is reduced to colorless compounds by reducing 
agents. 

Commercial alizarin is sold as a paste containing 20 per 
cent dry matter, representing nearly pure dyestuff, as a 
paste containing 40 per cent of dry matter, and as a 
powder containing 80 per cent or more of alizarin. Two 
essentially different shades of alizarin are distinguished, 
alizarin V (v = violet) or blue shade, and alizarin G (g — 
gelb = yellow) or yellow shade. Alizarin V is the purest 
commercial alizarin. Alizarin G is mainly a mixture of iso- 
and flavo-purpurin, containing some alizarin. It produces 
the most brilliant reds. 

Alizarin forms a number of insoluble lakes with calcium, 
aluminium, etc. 

Methods of Application. — Alizarin is applied to cotton 
by the following methods : — 


MORDANT DYESTUFFS 


205 


(1) The Turkey-red processes, which yield exceedingly 
bright and fast reds. Oils and aluminium salts serve as 
mordants. 

(2) Alizarin-red processes, in which the mordant is 
aluminium acetate. 

(3) Chromium mordants, for claret-red and maroons. 

(4) Iron mordants, for violets. 

Turkey-red Processes.—Turkey-red is the brightest and 
fastest, and at the same time the most expensive, red which 
can be produced on cotton. 

Like bleaching and other important processes, the 
methods for the production of Turkey-red vary in dif¬ 
ferent mills, and according to the results desired. 

Three processes for Turkey-red dyeing are in use. In 
all three, the material is treated with oil, which is fixed 
or made insoluble, and then caused to combine with the 
aluminium mordant, after which the dyeing follows. The 
difference lies in the use of different oils, and consequently 
different methods of fixing it. 

The emulsion or old process uses rancid olive oil. 

Steiner s process uses hot, clear olive oil. 

The new process uses Turkey-red oil. 

We will consider the last-named process only. 

New Turkey-red Process.—The operations are as fol¬ 
lows : — 

(1) Boiling Off. — The yarn or cloth is boiled off with 
caustic soda. 

(2) Oil Preparing. — The washed goods are hydro- 
extracted, but not dried, and are then worked in a bath 


20 6 


PRINCIPLES OF DYEING 


of io to 20 pounds neutralized Turkey-red oil (50 per cent) 
in 10 gal. water. 

Turkey-red oil consists of a mixture of fatty acids and 
their sulphates prepared by treating castor oil with sul¬ 
phuric acid, under suitable conditions, and partly neutraliz¬ 
ing the product with soda or ammonia. 

(3) Stoving .— The oiled goods are wrung evenly out 
and dried at a temperature of 40° to 6o° C. The Turkey- 
red oil is decomposed, ammonium sulphate and fatty acids 
being produced, which latter are fixed on the fiber by 
chemical decomposition. 

(4) Aluming. — The goods are worked 5 or 6 hours in a 
warm bath of aluminium acetate (red liquor), or of basic 
aluminium sulphate, wrung out, and dried. The basic 
aluminium sulphate is prepared by dissolving 4 parts alum 
in water, and adding to the cold solution 1 part crystallized 
sodium carbonate in solution. Aluminium compounds 
with the fatty acids are fixed on the fiber. 

For the production of a bright and intense red, the 
second, third, and fourth processes are repeated. 

(5) Chalking .—-The material is worked in a bath of 
finely ground chalk, when the alumina is precipitated in a 
basic condition, i.e. “ fixed.” Phosphate of soda and am¬ 
monium carbonate are also used as fixing agents. 

(6) Dyeing. — A bath is prepared with the desired 
quantity of dye (alizarin G), the goods entered at 25 0 , and 
turned 20 minutes; in half an hour the bath is heated to 
60 or 70°, and maintained at this temperature for an hour. 
After dyeing, the goods are wrung out and dried, with or 
without washing. 

It is essential that the dye-bath contain lime, though not 


MORDANT DYESTUFFS 


207 


too much. If the water used contains little or no lime, a 
suitable addition of ground and washed chalk may be 
made; a moderately hard water requires no addition. 
Very hard water, or water which contains iron, cannot be 
used in Turkey-red dyeing. 

After dyeing, the goods possess a dull red color, which 
is transformed by the processes which follow into the brill¬ 
iant Turkey-red shade. 

(7) Second Oil Preparing. — The material is impregnated 
with a solution of neutralized Turkey-red oil, and dried. 
This is often omitted. 

(8) Steaming. — To develop the color, the goods are 
steamed, with or without pressure. 

(9) Clearing. — The goods are worked twice in a soap- 
bath, sometimes warm, sometimes boiling. This removes 
loosely fixed dye, and fixes the remainder more permanently. 

Alizarin-red Processes. —The colors produced by these 
methods are cheaper, and inferior in brilliancy and in fast¬ 
ness to the Turkey-reds. 

With Aluminium Acetate. — The processes follow : — 

(1) Mordanting or padding with aluminium acetate. 

(2) “Ageing” in a warm room, basic aluminium acetate 
being formed. If the temperature is too high, the decom¬ 
position goes too far, and the mordant is “burned.” 

(3) “Fixing” in a bath of phosphate, arsenate, or sili¬ 
cate of soda, which removes the remainder of the acetic 
acid. Wash. 

(4) Dyeing in a bath containing Turkey-red oil, and 
sometimes some tannic acid as well as the dye. Wash and 
dry. 


208 


PRINCIPLES OF DYEING 


(5) Impregnation with Turkey-red oil, and drying. 

(6) Steaming, soaping, and drying. 

With Aluminate of Soda. — This process is usually 
applied to piece goods. The cotton is padded with alumi¬ 
nate of soda, dried, aged, and the aluminium fixed with 
ammonium chloride or silicate of soda, and then in a chalk- 
bath. It is then dyed, etc. 

Aluminate of soda is prepared by dissolving aluminium 
hydroxide in caustic soda : — 

Al(OH) 3 + 3 NaOH = Al(ONa) 3 + 3 H 2 0 . 

Erban and Spechfs Method. —( a ) For dark shades. 
The material to be dyed is impregnated with a solution of 
the color in ammonia, and dried, whereby the volatile sol¬ 
vent escapes, and the coloring matter is deposited in an 
insoluble form upon the fiber. A second impregnation 
follows with aluminium-acetate, after which the material is 
steamed, which expels the acetic acid and fixes the color- 
lake upon the fiber. 

(b) For light shades. The fiber is impregnated with a 
solution of aluminate of soda and the color in ammonia. 
The material is then steamed. If caustic soda is used, in 
any form, the steaming must be done with steam which is 
highly charged with acetic acid. 

Alizarin on Chromium Mordants. — The shades produced 
are claret-red and maroon. Alizarin B or V may be used. 
The former gives more brilliant and bluer tints. The 
process of mordanting usually used is as follows: — 

(1) Saturation once with a solution of neutralized Turkey- 
red oil, and drying. 

(2) Impregnation with tannin. 


MORDANT DYESTUFFS 


209 

( 3 ) Mordanting with basic chromium chloride, chromium 
acetate, or chromium mordant GA I. 

( 4 ) Washing with weak lime-water. 

( 5 ) Dyeing. The goods are introduced in the cold dye- 
bath, which is heated gradually to boiling (in an hour), 
and boiled two hours. They are then well rinsed in water, 
and finally soaped at 6 o° or at the boil, washed and dried. 

Methods rarely used are : — 

Erban and Spec/it's Method. —A solution of chromium 
hydroxide in ammonia replaces sodium aluminate used in 
mordanting with aluminium. 

Impregnation with Unstable Chromium Compounds. — In 
this case, the cotton is treated with a chromium compound 
which decomposes on the fiber, forming insoluble chromium 
hydroxide. The decomposition may take several hours. 
The cotton is then washed. The chromium compounds 
used are sodium chromite, chromium mordant GA I, and 
chromium bisulphite. 

Sodium chromite is prepared by dissolving chromium 
hydroxide in caustic soda : — 

Cr(OH ) 3 + 3 NaOH = Cr(ONa ) 3 + 3 H 2 0. 

Or by treating chrome alum or chromium acetate with 
a sufficient quantity of caustic soda solution to dissolve the 
precipitate first formed. 

Double Decomposition of Chromium Salts with Soda. — 
The material is impregnated with a salt of chromium, pref¬ 
erably a basic salt, dried, and passed through a boiling 
* solution of soda ash (sodium carbonate). Chromium hy¬ 
droxide is precipitated : — 

Cr 2 (S0 4 ) 3 + 3 Na 2 C0 3 + 3 H 2 0 = 2 Cr(OH) 3 + 3 Na 2 S0 4 
p +3 C0 2 . 


210 


PRINCIPLES OF DYEING 


The operations are repeated until sufficient chromium 
hydroxide has been deposited on the fiber. The chromium 
salts used are the sulphate, nitrate, chloride, acetate, or 
their basic salts, like Cr 4 (S 0 4 ) 3 ( 0 H) 6 . 

Alizarin on Iron Mordants.—Violet shades are produced 
by the use of iron mordants, alizarin V being used. 

One method consists in oiling with Turkey-red oil, mor¬ 
danting with pyrolignite of iron, fixing with a chalk-bath, 
and dyeing. 

By a second method, the cotton is mordanted with tannin 
and iron, and fixed with a bath of cow-dung, or with 
arsenate, phosphate, or silicate of soda. 

The dye-bath is made up with dyestuff and neutralized 
Turkey-red oil, the cotton introduced into the cold bath, and 
the temperature raised during hours to 75°. After dye¬ 
ing, the cotton is washed, dried, steamed, and soaped. 

Experiment 70. — Mordant a boiled-off skein of cotton yarn 
with 10 per cent alum and 2 per cent sodium carbonate in 200 cc. 
water, working 15 minutes. Squeeze, and work 10 minutes in 2 
per cent chalk in 200 cc. water. Wash and dye as directed below. 

Mordant a second skein by working 15 minutes in a solution of 
25 per cent ferric sulphate in 200 cc. water. Squeeze, and pass 
through lime-water. Wash. Dye both skeins as follows : — 

Prepare the bath with 20 per cent alizarin paste and 2 per cent 
chalk in 200 cc. water. Enter the cotton, work well, heat to boil¬ 
ing, and boil 30 minutes. Clear by boiling in a 1 per cent solution 
of soap. 

Test fastness to washing. What class of colors is this dye in ? 

Logwood. — Logwood is a very important dye for the 
production of blacks on cotton. Its properties and chem¬ 
istry have already been treated in Chapter V. 


MORDANT DYESTUFFS 


211 


The methods for dyeing logwood on cotton are illustrated 
by Experiments 30 and 31 (mordanting and dyeing), and 
Experiment 33 (single-bath method). Variations of these 
methods are in use, one of which is as follows: — 

The material is padded or steeped in an infusion on 
myrabolans (40 per cent), and squeezed; passed through 
weak lime-water, which forms calcium tannate; worked in 
“nitrate” of iron, or acetate of iron of 4 0 Tw.; passed 
through lime-water, which precipitates basic ferric tannate; 
washed thoroughly and dyed. 

Logwood extract is usually employed in cotton dyeing. 
The cloth or yarn is dyed with 30 to 50 per cent logwood 
chips, or 5 to 8 pounds extract, usually with the addition 
of fustic (a yellow dye) to modify the shade, and also a 
little copper sulphate. The dyeing is commenced cold, and 
the temperature of the bath raised slowly to the boiling- 
point. 

If the logwood black is to be very fast to washing, it is 
saddened after dyeing by passing through a hot, weak bath 
of potassium bichromate or nitrate of iron. In some cases 
the saddening is effected by adding ferrous sulphate to the 
dye-bath when the dyeing has been completed, and working 
about 20 minutes longer. The results are not as good as 
if a separate bath is used. 

The single-bath method does not yield colors so fast to 
rubbing as the two-bath method. 

Defects. — Rubbing is caused by too rapid fixation of the 
color, or by incomplete washing after mordanting. In the 
single-bath method, rubbing is due to superficial fixation of 
the color-lake. 


212 


PRINCIPLES OF DYEING 


Greening. — Logwood blacks sometimes become green 
after short usage; it is due to the use of too much bichro¬ 
mate of potash in the saddening bath. 

Tendering is caused by the oxidation of the fiber by an 
excess of bichromate. Rusty colors are due to over-oxida¬ 
tion of the coloring matter. 

Cutch. — Cutch, or catechu, is used for the production of 
browns on cotton. It is extracted from certain plants grow¬ 
ing in India, and occurs as irregular lumps of a brown color. 

Cutch contains a tannic acid known as catechu-tannic 
acid, which has a direct affinity for the cotton fiber. It is 
applied directly to the fiber, usually with the addition of a 
little copper sulphate. Potassium bichromate in a second 
bath produces the color-lake. For a full shade, the cotton 
is boiled with from 15 to 20 per cent cutch, and 1.5 to 
2 per cent copper sulphate. After standing for some 
time, it is worked in a hot bath of 2 per cent bichromate 
of potash, washed, and dried. 

Cutch is combined with logwood, fustic, and other 
mordant colors for compound shades; it can also be 
topped with basic colors, since it contains tannic acid. 

Other Mordant Colors. — Other mordant colors are ap¬ 
plied to cotton by the same methods as are used for aliza¬ 
rin, or logwood. 

Bisulphate compounds of certain alizarin colors may be 
applied in the same bath with a chromium mordant; the 
material is dried, and then steamed, which decomposes the 
bisulphite compound, and the insoluble chromium lake is 
formed. 

For example, cotton is evenly saturated with a solution 


MORDANT DYESTUFFS 


213 


of 10 lb. alizarin blue S in 8 gal. cold water, to which 
1 gal. chromium acetate 32 0 Tw. is added. The cotton is 
dried, steamed, washed, soaped, and dried. 

Alizarin indigo-blue S, alizarin green S, and cerulein S 
are applied in this way. 

Mordant Dyestuffs on Linen. — Mordant colors are 
largely applied on linen. The methods are similar to 
those used for cotton. 

Mordant Colors on Wool. — The mordant dyes are largely 
used on wool, the colors produced being very fast to air 
and light, dilute acids, alkalies, and to scouring. 

A prime necessity in applying mordant colors to wool is 
the thorough purification of the fiber from fatty and greasy 
matter. Any of these form sticky soaps with the mordants, 
which attract dyestuff, and afterward rub off. 

The mordant colors for wool are divided into two classes : 
ordinary mordant dyestuffs and acid mordant dyestuffs. 

Ordinary Mordant Colors. — These are applied by 
mordanting and dyeing, and by the single-bath method. 
The mordants are salts of aluminium, chromium, and iron. 

Mordanting with Aluminium. — Aluminium mordants 
are of limited application in wool dyeing, the only colors 
produced by its use being the alizarin reds and oranges, 
and alizarin maroon. 

The bath is charged with alum and an assistant, whose 
function is to prevent the alum from decomposing too 
rapidly, so that good penetration and even mordanting will 
result. The assistants used are tartar (cream of tartar), 
oxalic acid, sulphuric acid, and lactic acid, tartar being 
preferred. The quantity of liquid in the bath should be 


214 


PRINCIPLES OF DYEING 


between 30 and 50 times the weight of the wool. In too 
dilute solution, alum is decomposed too rapidly and fixed 
superficially, so that the colors are poor, and rub off. In 
too strong solution, the wool fixes too much acid along 
with the alumina, which hinders the lake formation during 
the subsequent dyeing process, so that the color produced 
is not very fast. 

The goods are entered at a low temperature, the tempera¬ 
ture raised gradually to the boil, and the bath boiled to 
2 hours. The amount of alum and assistants to be used 
depends on the depth of color desired: 6 to 10 per cent of 
alum and 5 to 8 per cent of tartar. For an example, see 
Experiments 28 and 71. 

For reds, neither the water nor the alum should contain 
even small quantities of iron, since it dulls the red. Copper 
should not come in contact with the bath for the same 
reason. The pipes for heating the bath may be of tin or 
tinned copper. 

Mordanting with Chromium. — Chromium is largely ap¬ 
plied for dyeing wool with mordant dyes. There are two 
methods of mordanting : — 

(1) The wool is boiled with a solution of potassium bi¬ 
chromate and an assistant, which may be tartar, oxalic 
acid, lactic acid, or sulphuric acid. The function of the 
assistant is to liberate chromic acid, which is taken up by 
the fiber. Tartar, lactic acid, and oxalic acid reduce the 
greater portion of the chromic acid to chromium hydroxide, 
while, when sulphuric acid is used, only a small portion 
of the chromic acid is reduced by the wool itself. Wool, 
properly mordanted with potassium bichromate and tartar 


MORDANT DYESTUFFS 


215 


or oxalic acid, is greenish in color, not yellow or brown. 
The different effect of the two assistants is shown clearly 
by Experiment 32. 

(2) Chromium fluoride (2 to 4 per cent) is used with 1 to 
2 per cent oxalic acid as an assistant. The chromium is 
fixed entirely in the form of chromium hydroxide. 

After mordanting, the goods are often allowed to lie 
over night before washing, when the mordant “ feeds,” 
that is, is further decomposed and absorbed by the fiber. 
Piece goods and skeins should be washed after mordant¬ 
ing, and never allowed to hang on poles or rails over night, 
as the mordant will feed on excessively at the lower points, 
causing uneven colors. The goods mordanted by the first 
method should also be kept moist and protected from 
direct sunlight, since chromic acid would be reduced in 
the dried and exposed portions, thus strengthening the 
mordant and causing uneven colors. 

Dyeing. — For aluminium mordants, the dye-bath should 
contain lime, preferably as calcium acetate, and an addi¬ 
tion of tannic acid is said to improve the fastness of the 
colors. For a full shade, 7.5 per cent acetate of lime and 
2 per cent tannic acid are used. 

For chromium mordants, the dye-bath is made slightly 
acid with acetic acid before the color solution is added. 
The objects of the addition of acetic acid are as follows: — 

(1) To correct the hardness of the water, and prevent 
the formation of insoluble calcium lakes. 

(2) To neutralize alkali present in many dyestuffs. 

(3) In slight excess, to facilitate the fixation of many 
dyestuffs. 


216 


PRINCIPLES OF DYEING 


The excess required is 2 per cent of the weight of wool 
over that required to neutralize the water and the alkali in 
the dye. Alizarin red, alizarin orange, alizarin brown, and 
gallein require a neutral bath, however, as the addition of 
acetic acid prevents the exhaustion of the bath. 

In dyeing, the wool is worked for fifteen minutes with¬ 
out heating, and then the temperature is raised very 
slowly, so that the bath boils in about an hour. The 
boiling-point must not be reached before the bath is 
nearly decolorized. To develop the color, and fix it 
thoroughly, 1J to 2 hours’ boiling is required. If the 
boiling is not continued long enough, the color will rub. 

Experiment 71. — Chrome Mordant. — Mordant a 5-gram wool 
skein by boiling half an hour in 3 per cent potassium bichromate and 
2 per cent cream of tartar in 200 cc. water. What color is it ? Dye 
in a bath of 10 per cent alizarin in 200 cc. water, boiling half an hour. 

Mordant a skein as directed above and dye with 2 per cent 
anthracene acid brown N. 

Mordant and dye with 2 per cent alizarin blue CS. 

Test fastness to washing. 

Alum Mordant. — Mordant a 5-gram skein of wool as follows : 
Boil half an hour with 6 per cent alum and 4 per cent sulphuric 
acid. Rinse, and dye with 10 per cent alizarin and l per cent 
chalk, boiling half an hour. 

Test fastness to washing. 

Saddening. — Full dark shades of certain colors, as 
alizarin brown, or alizarin red, may be saddened with J per 
cent bichromate of potash or 1 per cent copper sulphate, 
to make the colors faster to milling. 

Level Dyeing. — Level dyeing is promoted : — 

(1 ) By regulating the Temperature. — If the bath is 
heated up too rapidly, or the goods entered at too high 


MORDANT DYESTUFFS 


217 


a temperature, the combination of dye and mordant takes 
place too rapidly, and uneven colors result. 

(2) Use of Alkalies. — The alkalies form soluble salts 
with mordant colors, which are taken up very slowly 
by the mordanted wool; finally, by adding acetic acid, 
the bath is exhausted. For goods difficult to dye through, 
the following method is used: The dye-bath is charged 
with color and 2 to 3 per cent ammonia, the goods are 
then entered, the temperature raised to a boil, and acetic 
acid gradually added. In this manner, an equal penetra¬ 
tion with the dyestuff is obtained and more level shades. 
Hard water should be purified for use in this process. 

Defects in Dyeing. —Uneven dyeings may be due to un¬ 
even mordanting, caused by heating the mordant bath too 
rapidly, by the use of a too dilute mordant bath or too 
small a quantity of the assistant, or not working the goods 
sufficiently in the mordant bath. It may also be due to 
uneven dyeing. Rubbing may be due to the use of a too 
dilute mordanting solution, or not boiling long enough in 
the dye-bath. 

Single-bath Method.—The results by this method are 
not as good as by the preceding method ; there is also some 
precipitation of dyestuff in the form of insoluble lakes. 

Alum Mordant. — For light shades of alizarin the bath is 
prepared with 3 per cent alum, 2 per cent oxalic acid, some 
calcium acetate, and the necessary amount of dyestuff. 
The wool is entered at a low temperature, and the tem¬ 
perature raised slowly. The oxalic acid holds the color- 
lake in solution until it can be absorbed by the wobl. 

Chromium Mordant .—A number of mordant colors 


218 


PRINCIPLES OF DYEING 


which are not oxidized by chromic acid yield very good 
results by the single-bath method, using 3 per cent potas¬ 
sium bichromate and 2 per cent sulphuric acid for full 
shades. 

Chromium fluoride is also used as a mordant. 

Experiment 72. — Prepare a bath with 3 per cent alum, 2 per 
cent oxalic acid, per cent calcium acetate, and 10 per cent aliz¬ 
arin paste in 200 cc. water. Enter a 5-gram skein of woolen 
yarn, heat very slowly to boiling, and boil an hour. Test fastness 
to washing and rubbing. 

Prepare a bath with 15 per cent alizarin and 3 per cent sodium 
bichromate, and dye as directed above. Test fastness to washing. 

Mixing.— Ordinary mordant dyestuffs which require the 
same mordants, may be mixed and dyed in the same bath. 

Logwood. — Logwood is an exceedingly important dye 
for wool dyeing, especially for the production of black. 
Examples of the methods of applying it are given in the 
experiments in Chapter V. P'or a high degree of fastness, 
the dyeing is saddened. 

Acid-mordant Colors. — The acid-mordant colors are ap¬ 
plied to wool in exactly the same way as the acid dyes, 
using the same precautions to obtain level dyeings. The 
bath is usually exhausted. The dyed wool is afterward 
treated with metallic salts, which develop the color by 
changing the dyestuffs into insoluble, dark-colored, and 
very fast compounds. In some cases the change is due 
to oxidation by bichromate of potash; in other cases a 
metallic salt or lake is formed. The mordanting opera¬ 
tion may take place in the same bath as the dyeing, or in a 
separate bath. 


MORDANT DYESTUFFS 


219 


Single-bath Method. — When the dye-bath is exhausted, 
it is allowed to cool to about 65°, the mordant is added, and 
the bath heated up again. The dyeings obtained by this 
process in the case of certain coloring matters are apt to rub 
and appear speckled, because that portion of the dye which 
was not taken up by the material is precipitated by the 
mordant as a lake, which is fixed superficially on the fiber. 

Two-bath Method. — More time for entering and remov¬ 
ing the goods is required, but the baths may be used 
continuously. 

Experiment 73.— ( a ) Dye a 5-gram skein of wool with 3 per 
cent anthracene-acid yellow C and 5 per cent acetic acid in 200 cc. 
water, boiling half an hour. Rinse and mordant in a fresh bath with 
1 \ per cent potassium bichromate in 200 cc. water, boiling i hour. 

(b) Dye with 2 per cent Cyprus green R, 5 per cent Glauber’s 
salt, and 2 per cent acetic acid in 200 cc. water. Mordant with 
1 per cent copper sulphate and 1 per cent acetic acid. 

Test fastness to washing. 

Mixing and Shading. — In mixing to produce compound 
shades, dyestuffs which require the same mordant must 
be used. For shading it is best to apply level-dyeing acid 
colors which are not affected by the mordant employed. 

Mordant Colors on Silk. — The mordant colors are not 
applied extensively to silk, because they are more expen¬ 
sive to produce than other dyes, which, as a rule, are fast 
enough for all ordinary requirements. Silk has the power 
of decomposing mordants, and fixing the metal at the ordi¬ 
nary temperature. 

Mordanting. — The silk is wetted out in the mordant 
solutions by continued handling, and then allowed to steep 
for several hours, or preferably over night. It is then wrung 


220 


PRINCIPLES OF DYEING 


out, the mordant fixed if necessary, and finally it is washed 
thoroughly. The washing removes excess of acid, which 
tends to hinder the dyeing process, as well as any unfixed 
mordant which would cause the color to rub off. The mor¬ 
dant solutions may be freshened up and used continuously. 

The mordants used are as follows : — 

Aluminium Mordants. —(i) Basic aluminium sulphate 
is prepared by dissolving io oz. alum and i oz. soda crys¬ 
tals per gallon of water, and heating until the precipitate, 
which forms at first, has redissolved. 

(2) Basic aluminium nitrate-acetate, or “ nitrate mor¬ 
dant.” The solution should be 10 to 15 0 Tw. The alu¬ 
minium mordants are fixed by working, after mordanting, 
in a solution of silicate of soda of |° Tw. for 15 minutes. 

Chromium Mordants. —(1) Basic chromium chloride of 
5 2° Tw. is used. Fix with silicate of soda. 

(2) Chromium chromate. Chromium mordant GA III 
is diluted with four volumes water. Wash without fixing. 

Iron Mordant. — Basic ferric sulphate (“ nitrate of iron”) 
is used. Wash without fixing. 

Dyeing. —The dyeing is carried out in a bath containing 
\ to l its volume of boiled-off liquor. For dark shades, the 
bath is made slightly acid with acetic acid ; but since the 
addition of acetic acid accelerates the absorption of color¬ 
ing matter enormously, acetic acid is not added for medium 
or pale shades, or irregular colors may be produced. The 
silk is entered cold, and worked cold half an hour, then the 
temperature is raised to near the boil in an hour. The 
dyeing is continued an hour longer; the silk is then 
washed, soaped, and brightened. 


CHAPTER XIX 




INSOLUBLE COLORS 

The insoluble colors constitute a group whose members 
have little in common. Some of them could be classed as 
mordant colors. They are all formed in an insoluble 
form on the fiber. This group falls naturally into three 
classes: — 

(1) Oxidation colors , in which the dye is produced on the 
fiber by oxidation of soluble substances. Indigo, formed by 
the oxidation of indigo-white by the air, and aniline black, 
from aniline, are the members of this group. 

(2) Insoluble azo colors , which are produced upon the 
fiber by the combination of a diazonium compound with 
other organic compounds. Paranitraniline red is the most 
important member of this class. 

(3) Mineral colors , which are inorganic in nature, and 
are produced by chemical reaction directly upon the fiber. 
Examples: iron-buff, chrome-yellow. 

Oxidation Colors.—Aniline black is produced on the 
fiber by the oxidation of aniline oil by oxidizing agents; 
indigo, by the oxidation of indigo-white by the air. 

Aniline Black. — Aniline black is one of the most impor¬ 
tant black dyes. It became of commercial importance 
soon after i860, when aniline could be purchased at a 
reasonable price. The composition of aniline black is not 


221 


222 


PRINCIPLES OF DYEING 


certainly known; it varies according to the method of 
dyeing. Three compounds have been separated from it: — 

Emeraldine is the first product of oxidation. It is a 
green salt, the free base of which is blue. 

Nigraniline is found by the oxidation of emeraldine. It 
is a violet-black base, the salts of which are green. Acids, 
especially sulphurous acid, turn it green. 

Ungreenable black is formed by the oxidation of nigrani- 
line under proper conditions. It is a black mass, and its 
color is not affected by acids or sulphurous acid. It com¬ 
bines with metallic oxides, such as chromic oxide. 

Properties. — The chief constituents of aniline black are 
nigraniline and ungreenable black. If the former is pres¬ 
ent in any quantity, the black is changed to green by acids, 
especially sulphurous acid; and the same change takes 
place under use. To prevent “greening,” all of the ni¬ 
graniline must be oxidized to ungreenable black. The 
purer the aniline oil from which the aniline black is pre¬ 
pared, the more difficult it is to produce an ungreenable 
black. The less pure anilines do not, however, yield such 
a fine black as pure aniline. 

Application.—Aniline black is extensively applied to 
cotton. Salts of chromic acid and chloric acid are used 
as oxidizing agents, there being also necessary, in the case 
of the latter, the presence of metallic salts, such as 
salts of iron, copper, and vanadium, to act as carriers of 
oxygen. 

(a) Single-bath Method. — A mixture of aniline, acid, 
and chromates is prepared in such a manner that aniline 
black is slowly formed in solution, and the cotton gradu- 


INSOLUBLE COLORS 


223 


ally attracts the major portion of the color, for the most 
part mechanically. 

(b) Oxidation Black. — In this case, the color is not 
developed in the bath. After the material has been 
impregnated with the solution of aniline and oxidizing 
agent, it is hung in a warm, moist room, where the oxida¬ 
tion takes place very slowly. 

(c) Steam Black. — The color is developed very rapidly 
by a process of steaming. 

There is considerable variation in the methods used for 
the production of an aniline black. 

Production on Loose Cotton and Yarn. — Potassium or 
sodium bichromate is used as the oxidizing agent. Exam¬ 
ples of the methods employed are as follows: — 

(a) Single-bath Method. — For 100 lb. cotton use 10 lb. 
aniline oil, 15 lb. sodium bichromate, 40 lb. hydrochloric 
acid or 12 lb. sulphuric acid, and 160 gal. water. The 
dye-bath is filled with water, and the cold solution of ani¬ 
line oil with a part of the hydrochloric acid is first added, 
then the bichromate dissolved in a small quantity of 
water, and lastly the acid. The cotton is introduced into 
the cold bath and turned continuously; when the color 
becomes distinct, the bath is slowly heated to 50 or 6o° to 
develop the shade. The operation may last from 1 to 3 
hours. If the heating has been too short, the black is liable 
to turn green under the influence of acids. 

(b) Steam Black. — A steam black may be produced as 
follows: 6 lb. aniline, 9 lb. hydrochloric acid, and 12 lb. 
sulphuric acid are dissolved in 20 gal. water. Another 
solution of 12 lb. bichromate of soda and 20 gal. of water 


224 


PRINCIPLES OF DYEING 


is prepared. After allowing to cool, 4 quarts at a time of 
each solution are poured into a small vessel, and the yarn 
is rapidly passed through the bath in lots of 2 lb., with 
fresh additions of the two solutions after each lot; within 
1 or 2 minutes, the yarn becomes bronze-black. The ma¬ 
terial is then wrung out, and steamed 20 minutes at 3| lb. 
pressure, which process renders it jet-black and also un- 
greenable. 

Experiment 74. — Dissolve 10 per cent aniline oil (which is 
dissolved in 12 per cent hydrochloric acid) in water, add 15 per 
cent sodium bichromate and 6 per cent sulphuric acid, and make 
the volume of the bath 200 cc. Enter the yarn, work well, heat 
slowly to boiling, and boil half an hour. The yarn is harsh to the 
touch. Soften by soaping it at the boil in a 1 per cent solution of 
soap. 

Production on Cloth. — For cloth, the oxidizing agent 
usually used is sodium or potassium chlorate. Two pro¬ 
cesses are as follows : — 

(1) Dissolve 10 lb. sodium chloride and 10 parts ammo¬ 
nium chloride in 8 gal. water. Dissolve 10 lb. copper 
sulphate in 7 gal. water. Dissolve 35 lb. aniline salt in 
as little hot water as possible, and neutralize the solution 
with a sufficient amount of aniline oil, testing the solution 
with litmus. When all the solutions are perfectly cool, 
add the solution of aniline salt to that of the sodium chlo¬ 
ride and ammonium chloride, then add the copper sul¬ 
phate solution, and dilute to 14 0 Tw. The cloth is then 
impregnated with the liquid, hydro-extracted, and aged or 
steamed. When the liquid becomes dark, it is replaced by 
fresh liquor; the old liquor is filtered, and used again for 
diluting fresh solutions. 


INSOLUBLE COLORS 


225 


After ageing, the goods are treated at 8o° in a solution 
of 20 parts sodium bichromate, 5 parts soda, and 5 parts 
salt per 1000 parts water, washed, and steamed at 15 lb. 
pressure. 

(2) Prepare concentrated solutions of if lb. aniline salt 
in 1 gal. water, and 1J lb. ferrocyanide of potash in f gal. 
water, and i| lb. potassium chlorate in i| gal. water. 
Work the cloth in a mixture of the solutions in a jigger; 
steam for two minutes; then work hot in a jigger in a 
solution of 1 lb. bichromate of soda in 50 gal. water, dry 
and finish. 

Ageing Chamber. — Aniline black is usually aged in a 
special chamber (Fig. 20). The machine consists of a 
chamber provided with guide rollers for the cloth, and 
steam pipes for heating and for injecting steam. The 
cloth passes continuously through the apparatus. 

Topping Aniline Black. — Aniline black is sometimes 
topped with a weak solution of methyl violet to render it 
ungreenable, the green and violet uniting to form blue. 
In order to avoid tendering, a black is often produced by 
dyeing a light aniline black and topping with other blacks. 

Soaping. — Aniline black must be thoroughly soaped to 
soften the material. Soaping also neutralizes any traces 
of mineral acids which may not have been washed out. 

Defects in Dyeing Aniline Black. — Rubbing off of the 

color is due to too rapid oxidation in the solution. Green¬ 
ing is due to imperfect oxidation of the aniline. Tendering 
is due to : ( a ) over-oxidation of the fiber by the oxidizing 
agents; (b) drying of the material during ageing or before 
the acid has been washed off; (e) imperfect final washing. 

Q 


226 


PRINCIPLES OF DYEING 



Fig. 20. — Aniline black ageing chamber. 































































































































































































INSOLUBLE COLORS 


227 


Indigo. — Dyeing with indigo requires two operations: 
(1) preparing the indigo solution, or setting the vat, as it 
is called; (2) dyeing proper. 

Application to Cotton. — Three methods for preparing an 
indigo vat for cotton are in use : namely, the lime-copperas 
vat, the zinc vat, and the bisulphite vat. In all cases, the 
indigo must first be ground to a fine paste with water. 
Artificial indigo is now put on the market in the paste 
form. The chemistry of these processes has been dis¬ 
cussed in Chapter VI. 

Copperas Vat. — As an example, the following is given : 
4 lb. indigo are placed in 75 gal. water, 8 lb. copperas 
are then dissolved in it, and finally 10 lb. quicklime. The 
quantity of indigo varies from 2 to 7 lb. according to the 
shade to be produced, and the other ingredients are added 
in the same proportion. The vat is stirred well, and 
allowed to stand. In about 24 hours the vat should be in 
the proper condition for dyeing. If so, the liquor will be 
clear and of a brownish yellow color, and a bluish scum 
(“flurry”) appears on its surface. If the liquid appears 
greenish, the indigo has not been completely reduced, and 
more lime and copperas should be added to the vat. 

The copperas vat may be used about a month. If neces¬ 
sary, it may be strengthened by the addition of fresh quan¬ 
tities of indigo, lime, and copperas. When used up, the 
sediment is often dissolved in hydrochloric acid to recover 
the indigo which it usually contains. 

Zinc Vat. — The zinc vat may be made up in the fol¬ 
lowing proportions: Water, 1000 gal.; indigo, 30 lb.; 
zinc, 25 lb.; lime, 25 to 30 lb. The mixture is stirred 


228 


PRINCIPLES OF DYEING 


well during a period of 18 hours, and then allowed to 
settle. Too much zinc keeps the vat muddy owing to the 
liberation of hydrogen. After a day’s work its strength 
may be restored by the addition of fresh quantities of zinc, 
lime, and indigo. 

Hyposulphite Vat. — In this case, the reducing agent is 
a hyposulphite, made by the action of zinc on sodium 
bisulphite. It is customary to prepare a strong solu¬ 
tion of the reduced indigo, and add it to the bath as 
required. 

Reduced Indigo. — Boil 20 lb. finely ground indigo with 
20 gal. water, cool and add 25 lb. slaked lime in the 
form of a cream. Prepare a hyposulphite solution by 
mixing 80 lb. sodium bisulphite of yo° Tw. with 9 lb. 
zinc dust in a vessel kept cool by immersion in another 
vessel containing cold water. When the zinc has dis¬ 
solved, the hyposulphite is run into the indigo and lime 
mixture. The whole is stirred well at intervals until 
the indigo has dissolved, made up to 50 gal., and kept 
in casks protected from the air. Reduced indigo is 
placed on the market by the manufacturers of synthetic 
indigo. 

Preparing the Vat .—Water is run into the vat and 
heated to 50° or 6o° C.; some hyposulphite solution, pre¬ 
pared as previously described, is added, and then slaked 
lime. Reduced indigo solution is added in proportion to 
the shade desired to dye, the mixture stirred well, and 
allowed to settle half an hour. 

If the vat becomes oxidized, a little hyposulphite so¬ 
lution should be added until the yellow color of the 
solution is restored. The vat should be kept alkaline by 


INSOLUBLE COLORS 


229 


the addition of a little lime from time to time. The vat is 
strengthened by the addition of reduced indigo when neces¬ 
sary. The solution of sodium hyposulphite does not 
keep. 

The vat described above is the lime-hyposulphite vat. 
For the soda-hyposulphite vat, a solution of caustic soda is 
added to the hyposulphite solution, and caustic soda is 
used in place of lime in making up the vat. 

Dyeing. — Skeins are usually dyed by hand. The indigo 
vat is made deep enough for all the sediment to sink below 
the reach of the skein. Any scum on the surface of the 
vat is raked to one side, the skein immersed and turned 
for a moment or two, wrung out, and hung up for the color 
to develop. The depth of shade produced depends on the 
strength of the vat and the time of immersion. A single 
dip suffices for light shades; for medium or dark shades, 
two or more dips are used, as a deep shade produced by a 
single dip rubs badly. 

Warps are run through the vat on a frame similar to 
that used in warp-dyeing machines. Usually several in¬ 
digo vats are used and the warp frame is arranged to 
travel on a rail, so that it may be moved from one vat to 
another as occasion requires. 

Topping Indigo. — Indigo on cotton is sometimes topped 
with methyl violet or direct reds to get deeper as well as 
brighter and redder shades. 

Application to Wool. — For indigo on wool, the hypo¬ 
sulphite vat and the fermentation vat are used. 

In the latter, the reduction of indigo is effected by the 
fermentation of sugar from the starch of bran or flour, etc. 


230 


PRINCIPLES OF DYEING 


An example is as follows : — 

For a vat of about 700 gal., 6 lb. madder, 6 lb. molasses, 
15 lb. bran, 15 to 30 lb. soda, 10 to 15 lb. indigo (20 per 
cent), and 2 lb. slaked lime are added to the vat one 
by one; it is stirred well, and heated to 50° C. The 
vat is then covered up and allowed to rest a day; then 
again carefully stirred up, and again left to rest until the 
fermentation has reduced the indigo. This will be apparent 
by the change in color of the liquid from dull black to 
yellow. Lime is then added to check the fermentation, and 
the dyeing begins. 

Insoluble Azo Colors. — The insoluble azo colors are dyes 
produced in an insoluble form directly upon the fiber, and 
are used almost exclusively for cotton. The difficulty in 
producing them is to obtain a color which will not rub. The 
most important of these colors is paranitraniline red. 

Paranitraniline Red. — Paranitraniline red is produced 
by combining beta-naphthol on the fiber with the diazonium 
compound of paranitraniline hydrochloride in solution. 
The latter is prepared by treating paranitraniline hydro¬ 
chloride with nitrous acid. There are two steps in the 
process : (1) impregnating and (2) developing. 

Impregnating. — A solution of sodium beta-naphtholate 
is prepared by dissolving beta-naphthol in caustic soda. 
Turkey-red oil or castor-oil soap is usually added to the 
solution to make the color brighter. The cotton is evenly 
impregnated with the solution, wrung out, and dried in a 
special oven where there is no danger of contact with acid 
fumes, which would decompose the sodium beta-naphtho¬ 
late and cause the dyeing to spot. After the material is 


INSOLUBLE COLORS 


231 


dry, it should be developed as soon as possible, as sodium 
beta-naphtholate is oxidized by the air, with the production 
of brown substances, and consequent irregularity in the 
shade. 

Yarn in skeins is impregnated in this solution in 2-pound 
lots at a time, as it is difficult to impregnate larger quanti¬ 
ties evenly, A portion of the warm solution is placed in a 
wooden bowl, 2 lb. of yarn passed through, another por¬ 
tion of the solution added, and another lot of yarn passed 
through, until 100 lb. have been impregnated. The yarn 
is then passed through once more, wrung, wrapped in thin 
calico and hydro-extracted, and dried at 148° F. for 3J to 
4 hours. 

Warps and cloth require a special impregnating machine, 
somewhat similar to the padding machine. 

Example. — For 100 lb. yarn , 2 lb. beta-naphthol are 
mixed with 0.7 lb. caustic soda and dissolved in 2 qt. 
boiling water; 5J lb. castor-oil soap are dissolved in 11 
qt. boiling water; mix and dilute to 12 gal. 

For cloth , 5 1 lb. beta-naphthol, 4 lb. caustic soda, and 
22 lb. castor-oil soap are dissolved in 55 gal. water. 

Developing. — The paranitraniline is dissolved in boiling 
distilled water with the addition of hydrochloric acid. Cold 
water is then added, which precipitates paranitraniline 
hydrochloride as a yellow paste. When the solution has 
thoroughly cooled, a solution of nitrite of soda is added. 
In about 10 minutes a clear solution of the diazonium com¬ 
pound results, which is kept as cool as possible. Just before 
the yarn or cloth is developed with this solution, the free 
hydrochloric acid (which prevents it from decomposing) is 
neutralized by the addition of a solution of sodium acetate. 


232 


PRINCIPLES OF DYEING 


Decomposition of the solution is indicated by the evolution 
of gas. If any free hydrochloric acid is present when the 
cloth is developed, the color will rub. The solution may 
be tested with paper colored with congo red; free hydro¬ 
chloric acid turns it blue. An additional quantity of so¬ 
dium acetate should be added in such a case. 

The development takes place in the same way as the 
impregnation. 

Example . — For ioo lb. yarn , dissolve i J lb. paranitrani- 
line in ij gal. boiling water and i-| qt. hydrochloric acid 
of 32 0 Tw. Add 3| gal. cold water. When cold, add a 
solution of 11 lb. sodium nitrite in 3 qt. water, with stir¬ 
ring. Dilute to 9o gal. with cold water. In another ves¬ 
sel, 4 lb. sodium acetate are dissolved in 11 qt. water. For 
developing, 4 parts of the first solution and 1 part of the 
second are used. 

For cloth the same proportions of materials are used. 

Experiment 75. — Prepare a solution of 9 per cent beta-naphthol 
(which is dissolved in caustic soda) and 20 per cent sodium car¬ 
bonate in 100 cc. water. Work in this a boiled-off skein of cotton 
for 5 minutes, remove, squeeze as evenly as possible, and dry. 

After the yarn is dry, prepare a solution of 3 per cent parani- 
traniline hydrochloride and 2 per cent sodium nitrite, and add 10 
per cent sodium acetate in a few moments. 

Immediately enter the prepared yarn, remove, wash, and dry. 
Test fastness to washing. What is the color ? 

Soaping. — After dyeing, the goods are washed well in 
cold water, and soaped with 2 per cent soap, which removes 
the loosely adhering particles of color. 

Defects. — Irregular or spotted dyeing may be caused by : 
(1) action of acid fumes upon the impregnated material; 


INSOLUBLE COLORS 


233 


(2) oxidation before developing, caused by slow drying or 
delay in developing; (3) uneven impregnation or uneven 
development. Unless properly applied, the color will rub. 

Other Colors. — 1 he other insoluble azo colors are pro¬ 
duced in a similar way to paranitraniline red; but as they 
are rarely used in dyeing, they will not be mentioned 
further. 

Mineral Colors. — Chrome-yellow, or lead chromate, has 
already been studied. Other mineral colors are manganese 
brown, iron-buff, and Prussian blue. 

Manganese Brown. —Manganese brown is a hydrate of 
manganese peroxide, and is produced by precipitating man¬ 
ganese hydroxide on the fiber and oxidizing it: — 

MnCl 2 + 2 NaOH = Mn(OH) 2 -f 2 NaCl. 

Mn( 0 H) 2 + 0 = Mn 0 3 H 2 . 

The color is very fast to light and washing. 

Production on Cotton. — The cotton is passed through a 
solution of manganous chloride which has been neutralized, 
if necessary, and then through a hot solution of caustic 
soda. It is then passed through a weak solution of chloride 
of lime or bichromate of potash to complete the oxidation. 

Iron-buff and Nankin Yellow. — These are composed of 
hydrated ferric oxides. They are produced by precipitat¬ 
ing a ferric salt on the fiber with an alkali or alkaline 
carbonate: — 

Fe 2 (S 0 4 ) 3 + 6 NaOH = 2 Fe(OH) 3 -f 3 Na 2 S 0 4 , 

or by precipitating a ferrous salt in the same way, and oxi¬ 
dizing the ferrous hydroxide. The colors are fast to light 
and washing. 


234 


PRINCIPLES OF DYEING 


Production on Cotton. — The material is saturated with a 
solution of nitrate of iron (3 0 to 6° Tw.), and then passed 
through a weak solution of caustic soda, lime-water, or 
chalk. The two operations are repeated till a sufficient 
depth of color is produced. 

Prussian Blue. — Prussian blue is ferric ferrocyanide. It 
is fairly fast to light and washing. 

Production on Cotton. —The cotton is dyed iron-buff, and 
then passed through an acidified solution of potassium (or 
sodium) ferrocyanide (yellow prussiate of potash). The 
depth of color depends on the quantity of ferric oxide on 
the fiber. 

Production on Wool. — The Prussian blue is formed by 
the decomposition of potassium ferrocyanide with acids. 
The wool is dyed in a bath of 10 per cent potassium ferro¬ 
cyanide and 20 per cent sulphuric acid, boiling an hour. 
Prussian blue is formed, and absorbed by the wool. 


CHAPTER XX 


MERCERIZATION-ARTIFICIAL SILK 

Mercerization (see Chapter VII) consists in the treat¬ 
ment of cotton with strong solutions of caustic soda fol¬ 
lowed by a thorough washing. Under ordinary conditions 
the cotton shrinks in length, but if the treatment and 
washing are conducted under tension, the cotton does not 
shrink, and receives an increased luster. 

The applications of mercerization are as follows: — 

(1) To produce embossed effects on cloth. 

(2) To impart a luster to cotton (artificial silk). 

Production of Embossed Effects. — Embossed or relief 
effects are produced upon cloth in two ways: — 

(1) The design is woven with wool and cotton, and the 
cloth mercerized. The cotton contracts, causing the wool 
to stand out. The operation must be conducted at a low 
temperature to avoid injuring the wool. 

(2) The caustic soda is printed upon the cloth in stripes 
or other designs. The printed parts contract, causing the 
other parts to appear in relief. If afterward dyed, the 
mercerized fibers take up more of the dye than the other 
portions, producing a colored design. A variation is to 
print the cloth with something which will protect it from 
the action of caustic soda, such as wax or oil, and then 
mercerize the cloth. 


235 


236 PRINCIPLES OF DYEING 

Production of Lustered Cotton. — The most important 
application is to impart a luster to cotton. The yarn is 
mercerized under tension. The conditions which influence 
the production of the luster are as follows: — 

(1) Quality of the Cotton. —The higher the quality of 
the cotton the better the luster. While all cotton increases 
in luster, the most silky appearance is imparted to high 
grades, as Sea Island and Egyptian. 

(2) Twist of the Cotton. — A soft twist is more favorable 
than a hard twist. 

(3) The greater the tendency to contract , and the more 
effectually contraction is prevented , the better the luster .— 
More tension than is required to prevent contraction is not 
necessary, and may result in rupture of yarn or cloth. 
The factors which influence the contraction are as fol¬ 
lows : — 

(a) The degree of contraction depends upon the strength 
of the mercerizing liquid : — 

Specific gravity . . . 1.07 1.11 1.19 1.25 

Contraction, per cent .1 16 22 23 

( b ) The contraction decreases as the temperature rises: — 

Temperature . . . i8°C. 30° C. 8o° C. 

Contraction, per cent 22 22 15 

( c) The time of contact has little effect. 

(4) Mechanical manipulation , such as beating, pressing, 
etc., are of no value. 

(5) Uneven mercerization will take place if the material 
is not completely saturated with the caustic soda; if such 
goods are dyed, it is almost impossible to get a uniform 
color. 


MERCERIZATION — ARTIFICIAL SILK 


237 


Process of Mercerization. —The cotton is first thoroughly 
wetted out, and then brought in contact with caustic soda 
of from 1.11 to 1.20 sp. gr., in appropriate apparatus for a 
few minutes, removed, and washed carefully. In most 
cases, the last traces of alkali are neutralized with a little 
acid. The first wash waters should be saved and used in 
preparing fresh solutions of caustic soda. 

Machinery for Mercerizing. — Machines for mercerizing 
should impregnate the material as evenly as possible with 
the mercerizing liquid, and prevent contraction as far as 
possible; a large number of machines have been patented. 
For even mercerization, it is essential that the material 
should be carefully wetted out. 

Skeins. — Machines for mercerizing skeins are of two 
types : — 

(a) The first type consists essentially of pairs of iron 
rods on which the skeins are placed, and which are then 
moved apart until the desired tension is obtained. The 
skeins are then immersed in the mercerizing liquid. The 
rods are made to revolve in the caustic soda, so that all 
portions of the yarn will come in contact with the merceriz¬ 
ing liquid. After mercerizing and washing, the yarn is 
removed. 

(i?) The skeins are placed over a circular, perforated 
drum, which can revolve at a high rate of speed, and is 
surrounded by a mantle. The drum is revolved, and 
caustic soda solution introduced; the centrifugal force 
causes it to penetrate all parts of the yarn. The yarn is 
then washed with water and removed. This machine 
allows some contraction to take place. 


238 


PRINCIPLES OF DYEING 


Warps. — The machine resembles a warp-dyeing ma¬ 
chine with two compartments, but is provided with a pair 
of heavy rollers where the warp enters, whose pressure 
may be regulated by a lever and weights to produce the 
desired tension. Each compartment is provided with a 
pair of squeezing rollers. The warps are pulled between 
the tension rollers by the squeezing rollers, through the 
solution of caustic soda, between the squeeze rollers and 
through the second compartment, which contains rinsing 
water, and between the final squeezing rollers. A jet of 
water just before the last pair of rollers aids in complete 
washing. 

Cloth Mercerizing. — The cloth is wound on a roller, and 
passes through one pair of rollers into the caustic soda, 
through a second pair of squeeze rollers into water, through 
a third pair, then is wound on another roller. The tension 
of the rollers is adjusted so that the material cannot con¬ 
tract. 

Properties of Lustered Cotton. — Cotton mercerized under 
tension (lustered) and without tension is the same chemi¬ 
cally and, with a few differences, physically. 

Lustered cotton is stronger than ordinary cotton, but 
weaker than cotton mercerized without tension. The 
effect of the tension is shown in the microscopic appear¬ 
ance of the fiber. Lustered cotton appears as a straight, 
translucent tube, with a small, round central opening. 
The luster is probably due to the fact that the surface of 
the cotton becomes smooth, thereby reflecting light in one 
direction instead of scattering it. 

Mercerized cotton has a much greater affinity for dyes 
and mordants than ordinary cotton. 


MERCERIZATION —ARTIFICIAL SILK 


239 


Dyeing Mercerized Cotton. — Mercerized cotton has a 
much greater affinity for dyestuffs, and absorbs them more 
rapidly and more completely from solution, than ordinary 
cotton. It also requires a smaller quantity of dye, from 
30 to 40 per cent less with dark shades (see Exps. 46, 
47, 48). Mercerized cotton is usually dyed with direct 
cotton colors, since these affect its luster least. 

On account of its affinity for dyes, precaution must be 
taken that the color is not absorbed too rapidly, producing 
uneven shades. 

Direct Cotton Colors. — The bath is made up with the dye 
and a portion of the salts required; the material is entered 
into the lukewarm bath, worked for about 20 minutes, 
then the remainder of the salts are added, and the dyeing 
finished in a bath heated from 40° C. to boiling, according 
to the depth of color. Turkey-red oil added to the bath 
assists in producing level colors. 

Basic Colors. — These produce more brilliant colors than 
the direct cotton colors. The mordanting takes place as 
usual, excepting that from one-quarter to one-third less 
tannic acid or antimony salt than for ordinary cotton must 
be used, owing to the greater affinity of the mercerized 
cotton for tannic acid. The yarn should be washed well 
before dyeing. 

To produce level colors, the dyeing must be conducted 
in a cold bath, acidified with acetic acid; it is also well to 
add the dyestuffs in two or three portions. 

In dark shades, the exhaustion of the dye-bath may be 
completed by heating it to 50° or 6o° C. toward the end of 
the operation. 


240 


PRINCIPLES OF DYEING 


Scroop Feel. — It is sometimes desirable to impart to 
mercerized goods the “ scroop ” feel of silk. Bleached 
yarn receives this property more easily than unbleached. 

(1) Bleached Yarn . — The yarn is worked in a cold soap- 
bath, passed through water, worked several times in water 
strongly acidified with acetic or tartaric acid, and dried 
without washing. 

(2) Unbleached yarn is treated with pure calcium acetate, 
then worked in a soap-bath, and finally in a bath containing 
acetic acid. 

Level Dyeing. — The following circumstances aid in level 
dyeing: — 

(1) Even Mercerization. — It is impossible to dye evenly 
material which has been mercerized unevenly. 

(2) Raising the Temperature of the Bath slowly. — The 
rate of absorption of the dyestuff increases with the 
temperature. 

Artificial Silk. —Two varieties of artificial silk are assum¬ 
ing commercial importance : namely, cellulose silk prepared 
from cellulose, and gelatin silk, from gelatine. 

In spinning the fiber, the solution of the material is 
forced through very fine tubes; it is caught on an endless 
belt, and solidifies. The fineness of the tubes and the rate 
of motion of the belt regulate the size of the fiber. 

Cellulose Silk. —The most important process for the 
manufacturing of artificial silk, and the one which has 
found the widest practical application, is the Lehner or 
Chardonnet process. 

Cotton is first converted into nitro-cellulose (Chapter 
VII) by treatment with a mixture of sulphuric and nitric 


MERCERIZATION — ARTIFICIAL SILK 


241 


acids, and dissolved in a mixture of alcohol and ether. The 
solution is forced through fine glass tubes, when the sol¬ 
vent evaporates, leaving a fine thread of nitro-cellulose. 
It is dried in a warm room, and, since nitro-cellulose is very 
inflammable (guncotton), it is denitrated or converted into 
cellulose by treatment with ammonium sulphide. 

Properties. — Collodion silk, as it is sometimes called, is 
a silk-like substance with a high luster and soft feel. It 
contains very little nitrogen. When wetted, it swells up 
and becomes very soft and weak, and it must be handled 
with caution in dyeing. 

Dyeing. — Cellulose silk has a great affinity for direct 
colors and basic colors, and precautions are necessary for 
obtaining level colors. Direct cotton colors are applied 
with the addition of soap and soda, or Turkey-red oil. 

Basic colors do not require a mordant. They are applied 
in a cold or warm bath (6o° C.). To produce level dyeings, 
the solution of the dye should be added in several portions, 
and the absorption retarded by the addition of 1 to 3 per 
cent acetic acid. 

Detection. — Cellulose silk may readily be detected in 
silk or wool by boiling the material with a solution of 
caustic potash. Silk or wool dissolves, but cellulose silk 
does not dissolve, even after prolonged boiling. 

Gelatin Silk. — This is spun from a solution of gelatine 
in hot water. When the threads are dry, they are exposed 
to vapors of formaldehyde, which combines with the gela¬ 
tine and renders it insoluble in water. 

The fiber has a high luster. Like cellulose silk, it tears 
with the greatest readiness when wet. 

R 


CHAPTER XXI 


DYEING OF UNION GOODS 

The methods of dyeing goods composed of two or more 
kinds of fibers vary according to the effect desired and 
according to the character of the goods. It may be de¬ 
sired (i) to produce a uniform color, or (2) to produce 
different colors on the two fibers (two-colored effects or 
changeants). The three classes of material to be dyed 
are cotton and wool, cotton and silk, and wool and silk. 
The dyeing may take place in a single bath, or by means 
of two baths, one of which dyes one fiber more or less 
completely, and the other completes the dyeing. 

The direct colors for each class may be divided into 
groups according to their behavior to both fibers in the 
same bath; the members of the group depend upon the 
class of material to be dyed, and to some extent upon 
the conditions of application. 

As an example of the classification, the grouping of the 
colors for dyeing cotton-wool goods is given : — 

Group I. Colors which dye both cotton and wool the 
same shade. 

Group II. Colors which dye cotton a deeper shade than 
wool. 

Group III. Colors which dye wool deeper than cotton. 

Group IV. Colors which dye cotton and wool different 
hues. 

242 


DYEING OF UNION GOODS 


243 


Group V. Acid colors which dye wool in a neutral bath 
without dyeing cotton. 

The affinity of the dye for one or the other fiber may be 
controlled to a great extent by varying the temperature of 
the dye-bath, etc. 

Experiment 76. — Group I. Make up a bath of 2 per cent 
Chicago blue 6 B and 10 per cent Glauber’s salt in 400 cc. water. 
Dye a 10-gram skein of cotton and a 5-gram skein of wool in the 
same bath. Dye half an hour at a temperature near the boil. 

The cotton and wool are dyed nearly alike. By regulating the 
temperature, both fibers may be caused to assume the same shade. 

Group II. Dye with 2 per cent curcumine S and 10 per cent 
Glauber’s salt in a boiling bath. Dye as directed above. The 
cotton is dyed darker than the wool. 

Group III. Dye with 2 per cent congo orange R and 10 per 
cent Glauber’s salt in a boiling bath. The wool is dyed darker 
than the cotton. By dyeing at a lower temperature, equal colors 
may be produced on the two fibers. 

Group IV. Dye with 2 per cent zambesi black F and 10 per 
cent Glauber’s salt. The wool and cotton are dyed different 
shades. 

These dyes are all direct cotton colors. 

Cotton-wool Goods. — The following methods are avail¬ 
able : — 

(1) Dye the cotton and wool in the same bath with 
direct colors (direct cotton colors, alone or mixed with acid 
colors which dye wool in a neutral bath). 

(2) Dye the wool with acid colors, then the cotton with 
direct cotton colors. The cotton can be topped with basic 
colors in the same or a different bath. 

(3) Dye the cotton, then dye the wool with acid colors. 
This method is called cross-dyeing in an acid bath, and the 














244 


PRINCIPLES OF DYEING 


colors on the cotton must have great fastness to boiling 
water and acids. 

(4) Dye the wool with acid colors, mordant the cotton, 
and dye with basic colors. 

(5) Mordant the cotton, and dye cotton and wool with 
basic colors. 

Dyeing with Direct Colors. —The rapidity with which 
the direct colors go on the fibers varies with the condi¬ 
tions, as follows: — 

(1) The higher the temperature of the dye-bath, and 
the stronger the boiling, the deeper will the wool be dyed. 

(2) The lower the temperature of the bath, the stronger 
will the cotton be dyed. 

(3) The affinity of the direct cotton colors to wool can 
be diminished by an addition of soda or borax to the bath. 

The baths do not exhaust, and should be kept as con¬ 
centrated as possible. 

Application. ( 1 ) Dyeing the Cotton and Wool the Same 
Color. — Dyes are used which dye the cotton and wool the 
same shade (Group I), or a combination of dyes which dye 
cotton deeper than wool (Group II), and those dyeing wool 
deeper than cotton (Group III). The bath is prepared 
with 3 oz. calcined Glauber’s salt per gallon water. The 
dye-bath is boiled, steam is shut off, the material entered, 
and run one-half to three-quarters of an hour without steam. 
A sample is then examined. If the shades of the cotton 
and wool are both too light, another addition of the dye¬ 
stuffs used for each fiber is made. The bath is then boiled 
up again, and the material worked another quarter to 
one-half an hour; a second sample is then taken. Should 


DYEING OF UNION GOODS 


245 


the wool appear too light, or of a different hue from the 
cotton, add some of the dyestuffs used for shading the 
wool (Group V), and boil up again. If the cotton is too 
light, or off color, the dyestuffs necessary for the cotton 
(Group II) are added, without raising the temperature. In 
dyeing deep shades, it is better to add one-fourth the dye¬ 
stuffs at a time, as the wool may take them up too rapidly 
otherwise. 

(2) Dyeing the Cotton and Wool Different Colors. — The 
wool is first dyed in boiling solution with acid dyes which 
dye in a neutral bath (Group V), then steam is shut off, 
and the cotton dyed with dyestuffs of Group II. Or dye 
directly with a mixture of colors of Groups II and V at 
8o° to 90°. 

Acid Dyes.—Acid dyes which dye wool only are used 
in union dyeing. The cotton is dyed by means of other 
colors. The methods are used mostly for two-color effects. 

Method 1. — The wool is dyed in a boiling bath (acid) 
with acid dyes which do not dye cotton, rinsed in a bath 
containing a little ammonia, and the cotton dyed with 
direct cotton colors which do not dye wool (Group II). 
The colors may be topped with basic dyes. 

Method 2. — The cotton is dyed with direct cotton colors, 
diazotized, and developed, and soaped. The wool is then 
dyed with acid dyes in an acid bath. Other dyes suffi¬ 
ciently fast may be used for the cotton, such as Turkey- 
red. 

Basic Colors.—The methods are: (1) The cotton is 
mordanted, and both wool and cotton dyed with basic 
dyes in a warm bath. Janus colors may be used to dye 


246 


PRINCIPLES OF DYEING 


both wool and cotton in a neutral bath ; the basic color is 
then fixed on the cotton in a bath of sulphuric acid, tannic 
acid, and tartar emetic. 

(2) The wool is dyed with acid dyes, washed, and the 
cotton mordanted, and then dyed in a cold bath. The 
full depth of color must not be given the wool by the acid 
dyes, as it has a slight affinity for the basic colors in cold 
solutions, and its color is somewhat deepened in the sec¬ 
ond bath. 

The cotton is mordanted in the usual way when it is to 
be dyed with basic colors, excepting that the temperature 
of the tannin bath should not exceed 45 0 ; if it does, the 
wool fiber takes up some tannic acid, and the cotton comes 
out too light a color. The dyeing is effected in a neutral 
or slightly acid bath ; the goods are entered at about 40°, 
and the temperature gradually raised to the boil. 

With the Janus colors, the bath is prepared with 5 per 
cent zinc sulphate; after working the goods at the boil for 
five minutes, the solution of the dyes is added; in about 
20 minutes, 20 per cent Glauber’s salt is added, and the 
working continued an hour, or until the bath is nearly 
exhausted. The goods are then entered in a bath of 
sumac or tannin; after about 15 minutes, tartar emetic 
and sulphuric acid are added, and the bath warmed to 70°. 

Shoddy Dyeing.—Cotton-wool goods may be prepared 
from fresh stock, or from shoddy, in whole or in part. 
When soft woolen rags are shredded for the purpose of 
remanufacture, the product is shoddy ; it is always colored, 
and contains cotton thread. The cotton which has been 
twisted into knots, which happens often, is called burls. 


DYEING OF UNION GOODS 


247 


In order to produce light shades upon dark shoddy, the 
material can be stripped in several ways: by boiling with 
3 to 6 per cent sulphuric acid; by boiling with 6 to 12 per 
cent sulphuric acid and 3 to 6 per cent potassium bichro¬ 
mate, which oxidizes the color; or by reducing the color 
with hyposulphite of soda. In the latter case, two to three 
gallons hyposulphite solution (page 228) and one-half gallon 
acetic acid are mixed with a hundred gallons water. Which 
of these methods is to be preferred in any particular case 
depends upon the nature of the dye. 

The following are the principal classes of shoddy cloths 
met with on the market: — 

(1) Pure cotton warp with more or less dark shoddy 
weft. In dyeing these, it is chiefly a question of dyeing 
the cotton so as to make it invisible. 

(2) More or less shoddy under-weft with pure woolen 
face, or with union face. In dyeing these, it is a question 
of covering the cotton burls, which mostly appear on the 
back, so that they will appear as little as possible. It is 
sometimes very difficult to dye the burls properly, and it 
has then been found advisable to pick them out with burl¬ 
ing irons. In black dyeing, logwood on tannic acid and 
iron covers the burls very successfully. 

Methods of shoddy dyeing are otherwise the same as 
for other union goods. 

Cotton and Silk. — The dyes for cotton and silk are 
divided into four groups, Group V being eliminated. The 
direct colors are, as a rule, dyed in a soap-bath with the 
addition of phosphate of soda, Glauber’s salt, or common 
salt, and a little soda. The addition of Glauber’s salt 


248 


PRINCIPLES OF DYEING 


causes the dye to go on the fiber more rapidly, and facili¬ 
tates exhaustion of the bath; for pale shades, it is omitted. 
The addition of soap diminishes the rapidity of absorption 
of the dyestuff, and a large quantity of soap tends to leave 
the silk much lighter than the cotton. To obtain level 
dyeings with pale shades, the temperature of the bath 
must be raised very gradually. After dyeing, the silk is 
brightened with acetic acid. 

The desired shade is seldom obtained without topping 
with acid or basic colors. Basic colors dye both cotton 
and silk; acid colors dye the silk only. The topping is 
conducted in a bath slightly acidified with acetic acid, 
which should be cold or slightly warm for basic colors, 
and about 45 0 C. for acid colors. 

Tzvo-colored effects are produced (1) by dyeing with 
direct cotton colors, which dye cotton and silk different 
colors, and (2) by dyeing the cotton, diazotizing and de¬ 
veloping, and dyeing the silk with acid dyes. 

Wool and Silk. — For this class of dyeing, colors are 
divided into the following groups : — 

Group I. Colors which dye wool and silk the same shade. 

Group II. Colors which, in a boiling bath, dye wool 
deeper than silk. 

Group III. Colors which dye the silk in a cold bath 
without dyeing the wool perceptibly. 

Group IV. Colors which dye the wool and silk the same 
shade in a cold or slightly warm bath. 

Methods of Dyeing.—The acid dyes of Group I dye 
wool more rapidly at a boiling temperature, silk better at 
about 6o° C. 


DYEING OF UNION GOODS 


249 

The following methods are based on this circumstance:— 

(1) Make up the bath with one-half of the dye, enter 
the goods at 6o° C., bring to a boil, and boil about 15 
minutes. The dye goes mostly on the wool. Shut off 
steam, and add the remainder of the dye when the tem¬ 
perature reaches 6o° C., and work a half hour, when the 
silk will be covered. 

(2) Add all the dyestuffs to the bath, and dye the wool 
as directed above. Then top the silk with basic dyes at 
6o° C. 

(3) Dye as directed above, and dye the silk in a cold 
acid bath with colors of Group III. 

A few colors are dyed in a bath made alkaline with 
sodium phosphate, and containing soap. Alkali blue must 
be developed after dyeing. 

Direct cotton colors are dyed at the boil in a neutral 
bath with the addition of Glauber’s salt. Should the silk 
remain too light, the goods are allowed to cool in the bath, 
or are topped in a fresh bath with colors of Group III. 

For changeants, the wool is dyed first in a boiling bath 
with colors of Group II, and the silk dyed in a cold bath 
with colors of Group III. 


CHAPTER XXII 


DYE MIXING-DYE TESTING 

The Solar Spectrum. — White light, when passed through 
a prism, is decomposed into a band of many different 
colored rays, called a spectrum. A spectroscope is an instru¬ 
ment for decomposing light into its components, and con¬ 
sists of three parts : a tube provided with a narrow slit 
through which the light enters, and containing lenses for 
making the rays parallel, a prism for decomposing the 
light, and a telescope for magnifying the spectrum. In 
the direct-vision spectroscope, all these parts are inclosed 
in a straight tube. 

If sunlight is examined through a spectroscope, a number 
of dark lines are seen to cross the spectrum, which never 
vary in position, and serve to mark the position of colors. 
The colors in the spectrum, in the order in which they 
come, are as follows : — 

Red, orange-red, orange, orange-yellow, yellow, greenish 
yellow, yellow green, green, and blue green, cyan blue, blue, 
blue violet, and violet. None of these rays of light can be 
further decomposed. Figure 21 represents the solar spec¬ 
trum, showing the relative position of the fixed lines. 

Absorption-spectrum. — If a solution of a colored body 
is placed before the slit of a spectroscope, some of the 
rays of light are absorbed, or quenched, and the result is 
the absorption spectrum of that solution. An absorption- 

250 


DYE MIXING —DYE TESTING 


251 


spectrum may be represented by shading the portion of 
the spectrum which is absent. Figure 22 represents the 
absorption-spectrum of picric acid, a yellow dye. The 
solution of picric acid is yellow, not because it transmits 
yellow light only but for the reason that all the light 
which passes through the solution combines in the eye 
to produce the sensation of yellow. The same is true of 
other colored bodies. Two solutions may appear the same 
color, but have different absorption-spectra. They may 


A a B G d n E b 

f Q 1 












•c 

<u 

ft? 

T 

•3 

ft? 

2* s 2 

5 3| 

0 0 0 

Fig. 21 .- 

a 3 •“ s 

oa 'a 

- Solar specti 

T ^ 

Hi 

§ 

V 

* ® 

*> * 

•um. 

w ^ - % 

Blue Violet-* 

Violet - 


transmit different rays of light which combine to produce 
the same color. 

A colored fabric behaves toward light exactly as if it 
were a colored solution. That is, a dye on a cloth has 
nearly the same absorption-spectrum as a solution of the 
dye of corresponding strength. 

Dichroism.—The absorption-spectrum of a colored solu¬ 
tion depends upon the strength of the solution used, or the 
thickness of the layer through which the light passes. A 
dilute solution usually allows more rays of light to pass 
through than a strong one; consequently the color of a 
solution may change according to its dilution. Chromic 
chloride is green in dilute solutions or thin layers, a claret- 


























252 


PRINCIPLES OF DYEING 


red in strong solutions or deep layers. Many dyes behave 
in a similar way. Methyl violet is bluish violet in dilute 
solution, claret in deep solution. Magenta is bluish pink 
in dilute solutions, red in strong solutions. Malachite 
green is blue green in dilute solution, reddish purple in 
very strong solution. This phenomenon is called dichroism. 

The same effects of selective absorption are observed 
when colors are dyed upon fabrics. Thus, it will be often 
found that reds, when diluted to make tints, assume an 
orange cast, and blues become greenish blues or reddish 
blues. 

Primary, Secondary, and Complementary Colors. — The 

human eye can distinguish but three simple or primary 
color-sensations : namely, red, blue, and green. All other 
colors can be considered as produced by admixture of 
these, and are called secondary colors. A mixture of red 
light and blue light produces violet light; blue lights and 
green lights produce blue green ; and red light and green 
light produces yellow. All three combine to make 
white. 

Complementary colors are two colors which when com¬ 
bined produce white. Every color which exists has its 
complementary color. The following pairs of colors are 
examples of complementaries : — 

Red and green blue, 

Orange and deep blue, 

Yellow and ultramarine blue, 

Green and red violet or purple. 

Hue, Tint, Shade, Purity. —The meanings of these terms, 
as used in exact color nomenclature, are as follows: — 


DYE MIXING—DYE TESTING 


253 


Hue is that which is generally understood by the term 
color , as red, yellow, blue, etc. 

Purity. —By the purity of a color is meant its freedom 
from white, or any other color, as a pure yellow, a pure 
blue. 

Tint. — The addition of successive quantities of white 
to a color produces a series of tints; there should be no 
variation in the hue of the color. Pink is a tint of red; 
cream, a tint of orange-yellow. 

Shade. — The addition of black to a color produces a 
shade. Maroon is a shade of red ; olive, a shade of yel¬ 
low green. Shades may be reduced by that addition of 
white, with the production of corresponding tints, as tints, 
of maroon, brown, etc. 

Absorption-spectrum of Mixtures. — When two colored 
solutions are mixed together, the resulting color is that 
which is transmitted by both colors in common. Thus, 
when yellow and blue dyes are mixed, green is produced, 

because green is the only color transmitted by each, all the 

* 

others being more or less absorbed or quenched. This is 
illustrated by Figure 22, showing the absorption-spectrum 
of a blue dye (indigo extract), and a yellow dye (picric acid), 
and the green produced by their mixture. The yellow dye 
transmits not only yellow but also red, orange, and green 
rays of light; the blue transmits blue and varying pro¬ 
portions of green, violet, and a little red light. Green is 
the only color common to both of them, and therefore 
freely transmitted. 

The color which will be produced by the mixture of two 
dyes depends, therefore, upon their absorption spectrum, 


254 


PRINCIPLES OF DYEING 


and is due to the combination of the rays of light which 
both dyes transmit. The color of the dye, while a guide, 
is no certain index to its absorption-spectrum, since two 
yellows, for example, may appear exactly alike, and yet 
absorb different rays of light. Mixed with the same blue, 
they will necessarily produce a different green. General 
principles, based on the color of the dye, may be laid down 



Fig. 22. — Absorption spectrum of a yellow dye (A), a blue dye ( B ), and their 

mixture ( C ). 


as an aid in their mixing, but there are only two ways to 
ascertain the exact color which will be produced : an ex¬ 
amination of the absorption-spectrum of the dyes, or experi¬ 
mental dye-trials with the mixture. 

Primary and Secondary Mixing-colors. — Experiments 
with dyes and pigments, which are explained by a study of 
their absorption-spectra, show that the following colors are 
produced by mixtures : — 





















































































































































































































































DYE MIXING —DYE TESTING 


255 


Red + yellow produces orange. 

Yellow + blue produces green. 

Blue + red produces violet. 

By varying the proportions of the red, yellow, or blue, 
innumerable gradations of hue can be obtained; thus, in 
the case of green, a series can be made ranging from yellow 
green on one hand to a green yellow on the other: — 

3 Yellow + blue = green yellow. 

2 Yellow 4- blue = yellow green. 

Yellow + blue = green. 

Yellow -f- 2 blue = blue green. 

Yellow + 3 blue = green blue. 

Similar variations may be made with the other colors. 

Red, yellow, and blue are the primary mixing-colors , 
while red, green, and blue are the primary colors. The 
difference is due to the fact that in one case we deal with 
the colors produced by the mixture of colored lights, and in 
the other case with the light transmitted by colored solu¬ 
tions. Red, yellow, and blue dyes mixed produce a black ; 
red, green, and blue lights combine to form a white light. 

Mixing of Dyes. — The following considerations are only 
aids in color mixing. Spectroscopic examination or dyeing 
tests.are necessary, as it is well known that two blues ap¬ 
parently similar may give with a yellow two greens of a 
very different cast. 

Green. — The most brilliant greens are produced by the 
use of a greenish blue with a greenish yellow. A reddish 
blue or yellow of an orange cast gives dulled greens, — 
citrine, etc. 


256 


PRINCIPLES OF DYEING 


Orange is best produced by combining a yellowish red 
(scarlet) with a yellow without a green cast. The purest 
oranges are not made by mixture. 

Violet. — Red of a bluish cast and blue of a reddish cast 
produce the best violet. Any yellow present dulls the color. 
The purest tones are obtained without mixture. 

Shades. — By mixing the three primary mixing-colors, 
shades of the different hues are obtained, the colors de¬ 
pending upon which primaries predominate. In mixing 
colors to produce shades, it is better to employ dull, sad 
colors than clear and decided primary colors, as the slightest 
excess of any one of the latter causes a great alteration in 
the mixed shade. Shades compounded of dull hues are 
more easily matched and kept on the proper standard. It 
is also desirable to use as few color constituents as possible 
to produce the desired result, as a variety of coloring matters 
produces complexity when the shade requires to be matched 
or altered to a desired standard. More than three or four 
colors is not necessary to produce any shade that may be 
wanted. 

The following are the principal shades produced by 
mixing colors with black : — 

Maroon from red; russet from orange; brown from orange- 
yellow ; olive from yellowish green ; sage from green ; slate 
from blue ; lavender from violet; plum from purple. 

As examples of color mixing to produce shades, the fol¬ 
lowing are given : — 

Red dyes mixed, in varying quantity, with black or green 
yield shades of red, ranging from claret through maroon to 
red black. 


DYE MIXING —DYE TESTING 


257 


Plum, brown, and olive are obtained by mixing orange, 
red, and green in various proportions. 

Olive is obtained by combining yellow, green, and 
orange. 

Tints. — Tints are produced by lowering the percentage 
of dyestuffs used. In making a series of tints, it will often 
be found that the Jiue changes, which must be corrected. 

Experiment 77. — (a) Dye cotton yam with 1 percent diamine 
red B, 1 per cent chrysamin G, and 3 per cent diamine blue 3 B 
with 20 per cent salt in 200 cc. water. Boil half an hour. Ex¬ 
plain result. 

(b) Dye with 1 per cent chrysophenin G, 1 per cent diamine 
blue 3 B, and 20 per cent salt. 

(<r) Dye with 1 per cent chrysophenin G, 1 per cent Chicago 
blue 4 R, and 20 per cent salt. 

(d) Dye with 1 per cent congo orange R, 1 per cent Chicago 
blue 4 R, and 20 per cent salt. 

(e) Dye with 1 per cent diamine red, 1 per cent chrysophenin 
G, and 15 per cent salt. 

(/) Dye with 1 per cent diamine red, 1 per cent diamine blue 
3 B, and 15 per cent salt. 

(g) Dye with 1 per cent catechu brown, 1 per cent diamine 
blue 3 B, and 15 per cent salt. 

Test fastness to washing of all the dyeings, and explain results. 
All the dyes named above are direct cotton colors. 

Effect of Light on Colors. — Colored bodies reflect only 
the light which they receive ; if the color of the light varies, 
their color will vary. If a series of the most beautiful 
colors is viewed by a pure yellow light, — such as may be 
obtained by the use of a sodium flame (burn an alcohol 
lamp containing a little salt dissolved in the alcohol), — 
all of the colors will appear yellow, or dull yellow or black. 


s 


258 


PRINCIPLES OF DYEING 


The color shown by a body is due to the combination of 
all the rays of light which it reflects. When the character 
of the light which illuminates the body is changed, it will 
no longer reflect certain rays of light, and the color of the 
body will change. Certain dyes and combinations of dyes 
are exceedingly sensitive in this respect. If the quality of 
the light which illuminates such a color changes in the 
slightest degree, — a tinge bluer or redder, — the whole 
aspect of the color changes. All such shades appear very 
red in gas or lamp lights, because these lights are deficient 
in blue rays; and flatter or bluer in a bluish light, such as 
comes from a clear sky, on account of the deficiency of red 
in such a light. 

It is possible, by combining specially selected dyestuffs, 
to produce two or three shades which will appear similar to 
each other in daylight, yet widely different by lamplight. 
Advantage has been taken of this property in producing 
fabrics which appear quite different in the day and at 
night. 

The dyer sometimes has great difficulty in matching com¬ 
pound shades which are so sensitive that their aspect varies 
with the slightest change in the quality of even the day¬ 
light. The color may be matched all right in the forenoon, 
and be sadly off in the afternoon. 

Such difficulties may be removed in two ways: — 

(1) By avoiding dyestuffs with very sensitive colors. 
This is not always possible. 

(2) By providing a light which does not change. The 
electric arc-light, shaded by colored glass so that its light 
will be the same as that of normal daylight, seems to give 
the best results in this respect. 


DYE MIXING —DYE TESTING 


259 


Color-blindness. — Color-blindness is the inability to dis¬ 
tinguish between certain colors, particularly between red 
and green. Pink appears blue; there is not much differ¬ 
ence between the color of a stick of red sealing-wax and 
grass by day. A florid complexion appears dusky blue. 
Sometimes the color-blind persons pick out the red color 
correctly, but after a while their eyes seem to become 
fatigued, and they commence to select wools of a different 
color, generally green, and place them on the red heap. 

Before beginning the study of dyeing, every student 
should be tested for color-blindness. He should be given 
a number of skeins of wool, and required to assort them 
according to their color, and he should also be required to 
name the colors of a number of samples. Ignorance of the 
names of colors should not, however, be mistaken for color¬ 
blindness. About one person in thirty or forty is color-blind. 

Dye Testing. — In order to ascertain the properties of 
a dye, its suitability for mixing, its fastness, etc., the dyer 
conducts experimental dye-trials by methods similar to 
those adopted for experiments in this book, using as nearly 
as possible the methods and reagents actually used in the 
dye-house. By such experiments, he is able to obtain 
results which may be applied to his practical work. For 
example, he may ascertain what dyes are necessary, and 
in what proportions, to produce a desired shade of a given 
degree of fastness. 

The methods for testing the fastness of a dye have 
already been given. 

Comparative Dye-trials.—The object of comparative 
dye-trials is usually to ascertain which of the two or more 


260 


PRINCIPLES OF DYEING 


samples of dyes is the least expensive. They may also be 
made to compare a sample of a dye with the consignment. 
Usually the samples are different samples of the same dye. 

Comparative dye-trials must be conducted under exactly 
the same conditions, if the two samples are samples of the 
same dye, as a slight variation in temperature or volume of 
water in one of the dye-baths causes a considerable differ¬ 
ence in the results. The amount of the dye used must 
not be large — not nearly sufficient to produce full shades; 
it is difficult to discriminate between deep shades of color, 
and again, if too much dye is used, much of it may be left 
in the bath, and probably in unequal quantities. As a rule, 
the methods to be followed should be similar to those used 
on a large scale. Fine woolen yarn is best for dye testing, 
even of dyes to be used on cotton, as it exhausts the bath 
more readily than cotton. 

There are two cases to be considered: (i) a comparison 
of money values, and (2) a comparison of coloring power. 
The first one is usually made by the dyer, the second one, 
by the dye dealer in testing his wares so as to bring them 
(by dilution) to a standard strength. 

(1) In comparing money values, simply dye equal weights 
of wool or cotton with quantities of dye in inverse pro¬ 
portion to their prices. For example, if two samples of 
fuchsine are to be compared, which cost 25 and 35 cents 
a pound respectively, we could make up a solution of 1 g. 
of each in a liter of water, and dye a 10-gram skein of 
wool with 50 cc. of the first, and = 35-5 cc. of the 

second. The skein which comes out darker would show 
which was cheaper. The purity of the color should also be 
considered. 


DYE MIXING —DYE TESTING 261 

(2) The relative coloring power is more difficult to as¬ 
certain. We would first dye two skeins with equal quanti¬ 
ties of the dyes say 50 cc. of the solution named above. 
After drying, the test is repeated, using 50 cc. of the weaker 
dye, and making three or more tests with the stronger one, 
using 25, 30, and 35 cc., or whatever volume that one 
judges would produce the same shade as the other. This 
is repeated until the two match. 

Experiment 78. — You will be given two samples of a basic dye. 
The tests must be carried out under as nearly the same conditions 
as possible. Weigh out very carefully i g. of each dye, and 
dissolve separately in 1000 cc. water, in a graduated flask, heat¬ 
ing if necessary. See that the solution is complete. 

Add 50 cc. of each solution, measured with a pipette, to two 
beakers, and make the volume of the solutions 200 cc. Place both 
beakers in the same water bath, heat to 6o° C., enter a skein of 
wool into each beaker, and heat for an hour. Remove, wash, dry, 
and compare the colors. 

If the colors are different, repeat, making one dyeing with one 
dye, and two or more with the other dye at the same time, using 
50 cc. of one dye and the quantity of the other dye that you think 
will give the same shade ; and also, in other beakers, 5 cc. less and 
5 cc. more than this quantity. Continue to test until you get two 
skeins to match exactly. Then the volumes of the two dyes re¬ 
quired to produce the same shade have the same coloring power. 
For example, if 50 cc. of A and 20 cc. of B are used, the strengths 
of A : B are as 20:50. 

Testing for Mixtures. — Many dyes on the market are 
mechanical mixtures of two or more colors. In some cases 
the mixture is made to produce a “ new ” dye. In other 
cases the mixture is made because the dyer wishes to pro¬ 
duce a certain color, and the quantity of one ingredient is 


262 


PRINCIPLES OF DYEING 


so small that it cannot be weighed accurately by the dyer 
himself. Mixtures may be recognized : — 

(1) By moistening a filter paper with water and blowing 
a small quantity of dye on it. Each particle of dye dis¬ 
solves with its own color, and it may be readily seen whether 
two or more colors are present. It is even possible to form 
an idea of the relative proportions of the different constitu¬ 
ents in this way. If the dye is insoluble in water, alcohol 
may be used. Valuable information may also be gained by 
dusting a few particles of the dye on concentrated sulphuric 
acid in a shallow dish, and observing the color with which 
they dissolve, which is usually different from that of the 
original dye. 

(2) By successive dyeings. If a small dye-bath is pre¬ 
pared and several skeins dyed successively therein, if the 
coloring matter is pure, it will give a shading down of the 
same color; but if it is not, the first and last dyeing may be 
quite different. In applying this test it must be remem¬ 
bered that many dyes come on the market in an imperfectly 
purified condition, and also that light and dark shades of the 
same dye may naturally differ somewhat in color (tone) as 
well as in depth of color. 

Experiment 79. — Test six samples of dye as follows : — 

Place a small quantity of the dye on a piece of paper, dip a filter 
paper in water, hold it up, and blow the dye on the paper. Each 
particle dissolves with its own characteristic color. 

Another way is to dust a little dye on the paper, and then wet 
it by floating it in a beaker of water. For dyes not soluble in 
water, alcohol may be used. 

Detection of Dyes. — The large number of artificial colors 
now on the market renders the identification of a particular 


DYE MIXING —DYE TESTING 263 

dye a matter of great difficulty. The color to be tested may 
be in the powder form or dyed on a fabric. In the latter 
case, the matter is still further complicated by the fact that 
few dyeings are made with a single color but mainly with 
mixtures. 

It is beyond the limit of this work to go into details in 
regard to this matter. The powder or fabric is subjected 
to the action of a number of reagents, and the behavior of 
the color noted. Parallel tests are then made with the dye 
suspected of being present. The reagents used are con¬ 
centrated sulphuric acid (see Exp. 12); dilute sulphuric 
acid or hydrochloric acid; dilute nitric acid; a solution of 
tannic acid and sodium acetate; reducing agents, as zinc 
dust and acetic acid (Exp. 3); sodium hydroxide and am¬ 
monia (Exp. 15); alum, potassium bichromate, ferric chlo¬ 
ride, stannous chloride, and bleaching powder. 

Except for the test with concentrated sulphuric acid, for 
which the dry powder is used, 1 g. of the dye should be 
dissolved or suspended in a liter of water, and portions of 
about 20 cc. taken for the tests. In the case of fabrics, 
portions of the material are cut off and subjected to the 
action of the reagents in porcelain evaporating dishes. 






INDEX 


Absorption-spectrum, 250, 253. 

Acid colors, 34, 195; defects in dyeing, 
199; exhaustion, 199; fastness, 201; 
level dyeing, 198. 

Acid-mordant colors, 202, 218; proper¬ 
ties, 195. 

Acids, action in dyeing, 30; on Biebrich 
scarlet, 30; on cellulose, 64; on silk, 
93; on wool, 83, 86. 

After-treatment, 175. 

Ageing chamber, 225. 

Alizarin, 204 ; application, 205 ; on chro¬ 
mium, 208; on iron, 210. 

Alizarin-red processes, 207. 

Alkalies, action on cellulose, 66; on silk, 
93 ; on wool, 83. 

Alkali blues, 33, 198. 

Alkali colors, 198, 201. 

Aluminate of soda, 208. 

Aluming, 206. 

Aluminium mordant, 190, 213, 220. 

Amaranth, 20. 

Amines, 18. 

Ammoniacal copper oxide, 60. 

Aniline black, 221; defects in dyeing, 
225; properties, 222; topping, 225. 

Animal fibers, 3, 78. 

Animalize, 24. 

Antichlorine compounds, 104. 

Antimony salts, 187 ; tannate, 25. 

Artificial mordant colors, 203. 

Artificial silk, 63, 240. 

Asbestos, 2. 

Assistants, 31, 40, 153, 167. 

Aureotin, 14. 

Azo colors, 221, 230. 

Basic aluminium sulphate, 206. 

Basic colors, 28, 183; after-treatment, 
190; composition, 183 ; defects in dye¬ 
ing, 191, 193; dyeing, 188; fastness, 


191. 193; properties, 183; topping 
with, 175, 181. 

Basic zinc chloride, 93. 

Bast fibers, 54. 

Bastose, 76. 

Baume hydrometer, no. 

Beaming, 70. 

Beta-naphthol, 17, 18, 172, 231. 

Biebrich scarlet, 29; stripping of, 31. 
Bleach, hydrogen peroxide, 126. 

Bleach, market, 112, 115; printer’s, 112; 

sulphur, 125; Turkey-red, 112. 
Bleaching, chemistry of cotton, 101; de¬ 
fects in, 116; electrolytic, 118 ; objects, 
100. 

Bleaching-powder, 103. 

Bleaching under sieve, 107. 

Boiled-off liquor, 129, 163. 

Boll, 54. 

Broad washing machine, 125. 

Burls, 246. 

Camel’s hair, 88. 

Campeachy wood, 35. 

Carbohydrates, 59. 

Carbonization, 65, 87. 

Carnotin, 14. 

Cashmere, 88. 

Catechu, 212. 

Celluloid, 63. 

Cellulose, 59; hydrate, 66; nitrates, 62; 
of linen, 74; silk, 240; solvents, 60; 
thiocarbonate, 62. 

Cerise, 20. 

Chargeants, 249. 

Chemic, control of the, 109; preparing, 
109; titration of the, no. 

Chemical theory of dyeing, 52. 
Chemicking, 106, 107. 

Chestnut extract, 185. 

China grass, 76. 


265 




266 


INDEX 


Chlored silk, 95. 

Chlorinated wool, 84. 

Chrome-yellow, 49. 

Chromium fluoride, 215. 

Chromium mordants, 208, 214, 220. 

Cloth bleaching, 112; drying, 149; dye¬ 
ing, 169; washing, 112, 114. 

Cocoons, 90. 

Collodion, 63. 

Color-blindness, 259. 

Color acid of congo, 8. 

Coloring matters, 3. 

Colors, feeding of, 155; matching, 157; 
mixing, 254; primary, secondary, and 
complementary, 252. 

Common salt, 168. 

Conditioning, 81, 92. 

Congo, 7. 

Cop, 70; bleaching, 109; dyeing, 144,169. 

Copperas vat, 47, 227. 

Cotton, 54; acid colors on, 195; tannic 
acid on, 186; basic colors on, 184; 
bleaching, 98, 100; composition, 58; 
count of, 71; detection of, 75, 87; 
direct cotton colors on, 165 ; fuchsine 
on, 24; Biebrich scarlet on, 31; fixing 
metallic mordants on, 38 ; grades, 55 ; 
manufacture, 70; mercerized, 67, 235 ; 
microscopic appearance, 56; mordant 
colors on, 203; tendering, 68; wax, 
58 ; wetting out, 99. 

Cotton-silk goods, dyeing, 247. 

Cottonwool and silk, estimation, 95. 

Cotton-wool goods, dyeing, 243. 

Coupling, 175. 

Count, 71, 88, 91. 

Crabbing, 125. 

Crystals carbonate, 168. 

Cutch, 212. 

Dash wheel, 115. 

Developers, 18, 172. 

Developing, 172. 

Diazonium compounds, 16. 

Diazotizing and developing, 16, 171. 

Diazotizing bath, control of, 172. 

Diazotizing, precautions in, 17. 

Dichroism, 251. 

Direct colors, 9. 

Direct cotton colors, 14, 164; after-treat¬ 
ment, 171, 175; application, 173; as 


mordants, 25; assistants for, 167; 
coupling, 175; defects in dyeing, 
176; diazotizing and developing, 171; 
exhaustion of, 169; fastness, 181; 
methods of dyeing, 165 ; mixing, 169; 
properties, 164. 

Decolorization, 102. 

Decolorizing agents, 103. 

Dolly, 124. 

Drying machines, 135 ; cans, 143. 

Dyes, classes, 51; for union goods, 242; 
comparative power, 259; detection, 
263; dissolving, 150; fastness of, 157; 
mixing, 156, 250, 255, 261; rate of 
absorption of, 154; retarding absorp¬ 
tion of, 133; testing for mixtures, 261. 

Dye testing, 259. 

Dye-bath, exhausting, 169. 

Dye-beck and wince, 145. 

Dyer, object of the, 1. 

Dye-spots, 27, 150, 161, 184, 191, 193, 199, 
200. 

Dye-trials, comparative, 259. 

Dye-vats, 136. 

Dyeing, control of salts in, 170 ; defects in, 
161,176,180,191,193,199, 217,225 ; ef¬ 
fect of metals in, 162 ; general observa¬ 
tions, 150; hand, 136; irregular, 200; 
laws of, 2 ; level, 153, 198 ; machinery, 
133; methods of, 195: objects of, 
98; preliminary operations to, 98; 
speckled, 200; standing baths in, 
155 ; theory of, 51; to shade, 156. 

Dyeing and mordanting, 41, 202. 

Ecru silk, 129, 130. 

Electrolytic bleaching, 118. 

Embossed effects, 235. 

Emeraldine, 222. 

Emulsion process, 205. 

Erban and Specht’s method, 208, 209. 

Eria silk, 96. 

Fastness, 13, 157; requirements for, 160; 
to acids, 13 ; to alkalies, 13 ; to bleach¬ 
ing, 158 ; to carbonizing, 158 ; to cross¬ 
dyeing, 157; to ironing and calender¬ 
ing, 158; to light, 13, 158; to milling, 
89; to perspiration, 13; to potting, 
158 ; to rubbing, 43 ; to storing, 158 ; 
to washing, 12. 




INDEX 


267 


Feeding, 155, 215. 

Fermentation vat, 48, 230. 

Fibers, behavior to mordants, 37 ; classes, 
3 ’ S3> 

Fibroine, 92. 

Filling, 70. 

Finishing, 70. 

Fixing, 25, 188. 

Flax, 73. 

Floret silk, 91. 

Flurry, 227. 

Frost, 69. 

Fuchsine, 20; printing, 27. 

Fugitive colors, 14. 

Fur, 78. 

Gallnuts, 185. 

Gelatin silk, 241. 

Glass wool, 2. 

Glauber’s salt, 168. 

Green, 255. 

Greening, 225. 

Grenadine, 20. 

Guncotton, 63. 

Haematin, 35, 39. 

Haematoxylin, 35. 

Hand dyeing, 136. 

Hard water, n, 151; action in dyeing, 
11, 27, 33, 164, 183; correcting, 151; 
effect on tannic acid, 186; softening, 
151 - 

Hardness, 11. 

Hawking machine, 148. 

Hemp, 76. 

Horn, 3. 

Hue, 253. 

Hydro-cellulose, 65. 

Hydro-extractor, 140. 

Hydrogen peroxide, 105,126 ; bleach, 126. 
Hydrometer, 109. 

Hydrosulphite, 47; vat, 47, 228. 

Indican, 44. 

Indigo, 44, 227; artificial, 45; carmine, 
hi, 159; composition, 44; dyeing, 
47, 228; extract, 49; reduced, 46, 
228; topping, 229. 

Indigo-white, 44, 45, 46. 1 

Indigotin, 44. 

Insoluble colors, 221, 


Insoluble azo colors, 230. 

Iron-buff, 233. 

Iron stains, 116. 

Iron tannate, 26. 

Imperial scarlet, 29. 

Irregular dyeing, 200. 

Janus colors, 189, 246. 

Jigger, 146. 

Jute, 75; bleaching, 119; dyeing, 196. 

Kemps, 80, 161. 

Kier, 99. 

Klauder-Weldon dyeing machine, 134. 

Lactic acid, 40, 213. 

Lake, 23, 25. 

Lanuginic acid, 84. 

Laps, 70. 

Lead chromate, 49. 

Leuco compounds, 21. 

Leuco-rosaniline, 22. 

Level dyeings, production of, 153, 169, 
198, 216, 240. 

Ley boil, 106, 114. 

Light, effect in dyeing, 157, 257; effect 
on colors, 257; fastness to, 13, 158. 
Lime boil, 112. 

Linen, 73; bleaching, 118 ; composition, 
74; detection of cotton in, 75; dye¬ 
ing, 75, 181, 213; microscopic appear¬ 
ance, 73. 

Lint, 54. 

Logwood, 35, 210, 218; application, 42; 
composition, 35; defects in dyeing, 
211; dyeing with, 41; extracts, 35, 
211. 

Loose cotton, bleaching, 106; dyeing, 133. 
Lustered cotton, 236. 

Madder, 204. 

Magenta, 20. 

Manganese brown, 233. 

Manganous chloride, 233. 

Manila hemp, 77. 

Market bleach, 112, 115. 

Mechanical theory of dyeing, 52. 
Mercerization, 66, 235; machinery, 237; 
uneven, 236. 

Mercerized cotton, dyeing, 239; proper¬ 
ties, 66; scroop feel, 246. 




268 


INDEX 


Metals, effect in dyeing, 162. 

Methylene blue, 64, 68. 

Methyl violet 5 B, 189. 

Mildew, 68. 

Milling, 80, 88. 

Mineral colors, 221, 233. 

Mineral fibers, 2. 

Mixing of dyes, 156. 

Mixtures, testing for, 261. 

Mohair, 88. 

Monogenetic colors, 40. 

Mordant dyes, 202; acid-mordant, 203; 
artificial, 203 ; level dyeing, 216; natu¬ 
ral, 203. 

Mordanting and dyeing, 41, 202. 
Mordanting with tannic acid, 187. 
Mordants, 24, 37, 67, 94; assistants for 
metallic, 40; behavior of fibers to, 37; 
behavior to mercerized cotton, 67; 
direct cotton colors as, 25; fixing, 
38; metallic, 37; sulphur, 192. 

Motes, 55, 161. 

Mungo, 87. 

Myrabolans, 185. 

Nankin yellow', 233. 

Naphthol green B, 85. 

Natural mordant colors, 202. 

New red L, 29. 

Nicholson's blue, 33. 

Nickel hydroxide, 93. 

Nigraniline, 222. 

Nitrate of iron, 132. 

Oil, in wool yarn, 123. 

Oil preparing, 205. 

Oil stains, 116, 161. 

Orange, 255. 

Orgazine, 91. 

Oxalic acid, 40, 213. 

Oxamine violet, 167. 

Oxidation, in bleaching, 117 ; colors, 221; 

of cotton, 69 ; of silk, 95 ; of wool, 85. 
Oxidation black, 223. 

Oxycellulose, 63; detection, 64; in 
bleaching, 105. 

Padding machine, 147; slop, 148. 
Paranitraniline red, 230; defects, 232. 
Para-rosaniline, 20. 

Parchment, vegetable, 62. 


Pastes, preservation, 203. 

Phenols, 18. 

Plan of study, 4. 

Ply, 72. 

Polychromin, 14. 

Polygenetic colors, 39. 

Potassium carbonate from wool, 122. 
Potassium permanganate, 105. 

Primary colors, 252. 

Primary mixing colors, 254. 

Primuline, 14. 

Printer's bleach, 112. 

Printing, fuchsine, 27; machine, single 
color, 148; stubbing and warps, 
149. 

Prussian blue, 234. 

Pulled wool, 78. 

Purity, 253. 

Purpurin, 204. 

Ramie, 76. 

Raw stock, dyeing, 133; drying, 134. 
Resin boil, 114. 

Resin soap, 114. 

Resorcin, 17. 

Retrospect, 50. 

Rosaniline, 20. 

Rubbing, 43, 161, 181, 191, 201, 211. 

Saddening, 42, 216. 

Salt, 168. 

Salting out, 7. 

Salts, control in dye-bath, 170; function 
in dyeing, 10, 198. 

Saponification, 101. 

Scarlet 3 RB, 29. 

Scarlet B, 29. 

Scouring machines, 124. 

Sea silk, 96. 

Secondary colors, 252. 

Secondary mixing-colors, 254. 

Sericinic acid, 93. 

Shade, 253. 

Shades, 256. 

Shoddy, 87, 246; cloths, classes, 247; 

dyeing, 246 ; stripping, 247. 

Silk, 90; acid colors on, 201; artificial, 
240; absorptive power, 94; basic 
colors on, 193; behavior of dyes to, 
94; bleaching, 130; boiling off, 129; 
brightening, 94, 163; cellulose, 240; 



INDEX 


269 


composition, 92; count of, 91; detect¬ 
ing wool in, 87; direct cotton colors 
on, 182; dyeing, 162; ecru, 129, 130; 
estimation, 95; glossing, 130; grades, 
91; gum, 92; lustering, 131; mor¬ 
dant colors on, 219 oxidation, 95; 
preparation of, 91; properties, 91; 
separation from cotton and wool, 
93; solution of, 93; souple, 129, 130; 
stretching, 130; tendering, 95 ; weight¬ 
ing, 131; wild, 96. 

Silk-cotton goods, dyeing, 247. 

Silk-wool goods, dyeing, 248. 

Silkworm, how it spins, 91. 

Single-bath method, 41, 202, 217. 

Sisal hemp, 77. 

Sizes, 98. 

Sizing, 70. 

Skeins, drying, 142; dyeing, 136; wash¬ 
ing, 138 ; wetting out, 99. 

Slag-wool, 2. 

Sliver, 70; dyeing, 135. 

Slop padding, 148. 

Slubbing, 88; dyeing, 135; printing, 
149. 

Soaping, 42, 162, 179. 

Soaps, 121. 

Soda ash, 168. 

Soda crystals, 168. 

Sodium acetate, 232; carbonate, 168; 
chlorate, 224; chromite, 209; hypo¬ 
chlorite, 104; nitrite, 17; peroxide, 
127; phosphate, 168; sulphide, 177. 

Sour, control of the, hi. 

Spectroscope, 250. 

Spectrum, 250; absorption, 250. 

Spun silk, 91. 

Stains, 116, 161. 

Standing baths, 155, 170. 

Steam black, 223. 

Steiners process, 205. 

Stoving, 125, 206. 

Straw, 3, 77. 

Stripping, 31. 

Substantive colors, 9. 

Suint, 82. 

Sulphur bleach, 125. 

Sulphur colors, 177; after-tieatment, 179; 
defects in dyeing, 180; methods of 
dyeing, 178 ; soaping, 179. 

Sulphur, detection in wool, 82. 


Sulphur mordant, 192. 

Sumac, 184. 

Sun hemp, 77. 

Tannic acid, 24, 184, 185, 215; absorp¬ 
tion by silk, 94; affinity for cotton, 
186; fixing, 25, 188 ; mordanting with, 
187; salts of, 186; weighting with, 
131; on wool, 86. 

Tartar, 40, 213. 

Tartar emetic, 187. 

Tender, 68. 

Tendering, 225 ; cotton, 68 ; linen, 74 ; 
of silk, 95; with sulphur colors, 180; 
of wool, 85. 

Textile fibers, 2. 

Theory of dyeing, 51. 

Thiochromogen, 14. 

Tint, 253. 

Tints, 257. 

Titration of the chemic, no. 

Toluene diamine, 17. 

Topping, 225. 

Topping indigo, 229. 

Tops, 79. 

Tram, 91. 

Turkey-red bleach, 112, 116; oil, 25, 190, 
206; processes, 205. 

Tussur silk, 96. 

Twaddle hydrometer, no. 

Twist, 71. 

Ungreenable black, 222. 

Union goods, dyeing, 242. 

Vegetable fibers, 3, 54. 

Vegetable parchment, 62. 

Violet, 256. 

Viscose, 62. 

Warps, 70; drying, 143; dyeing, 142, 
169; printing, 149; sizing, 143; wet¬ 
ting out, 99. 

Washed wool, 81. 

Washing machine, 112, 114. 
Water-proofing, Willesden process, 61. 
Water purification, 152. 

Weighting, 131. 

Woad, 44. 

Wool, 78; absorptive power, 86; acid 
colors on, 196; basic colors on, 191; 




INDEX 


270 


behavior to dyes, 86; bleaching, 125; 
chlored, 184; cloth, scouring, 124; 
composition, 82; dead, 80; detection 
of, 87; detecting cotton in, 87; di¬ 
rect cotton colors on, 181; extract, 
87; felting, 80; grades, 78; grease, 
122; indigo on, 229; microscopic 
appearance, 79; mordant dyes on, 
213; manufacture, 88; mordanting, 
37, 213 ; oxidation, 85 ; plasticity, 81; 
properties, 80; pulled, 78; silk, and 
cotton, estimation, 95; wool-silk 
goods, dyeing, 248; solution of, 83; 


detection of sulphur in, 82; sulphur 
in, 161; tendering, 185; vegetable, 
56; washing, 120; yarn, scouring, 
123; yarn, stretching, 123. 

Woolen yarn, 79. 

Worsted yarn, 79. 

Wringing, 140. 

Yarn, 70; bleaching, 106; impurities in, 

98. 

Yolk, 81. 

Zinc vat, 48, 227. 


Printed in the United Stales of America. 





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